248

Section 7 Technical Specification

of "Design, Supply, Erection, Installation, Testing and Commissioning 33/11KV

AIS Substation on Turnkey Basis Under Power Distribution System

Development Project, Rajshahi Zone (Package-AIS-4)"

249

7.1 TECHNICAL SPECIFICATIONS FOR 33/11 KV AIS SUBSTATION EQUIPMENT

250

TECHNICAL SPECIFICATIONS FOR 33/11 KV AIS SUBSTATION EQUIPMENT

7.1.1 Scope

This clause describes the General Technical Requirements for the new 33 KV VCB with PCM and 11KV AIS Switchgear and general switchyard equipment, and shall be read in conjunction with the Project Requirements, Schedules and Drawings in the specification.

The Contractor shall demonstrate that the switchgear has been designed, built and installed in accordance with the relevant international standards and the specification as specified in the tender documents. It shall also operate and perform on a site in accordance with the requirements of the specification and in the environment defined herein.

The design shall be proven by the submission at the time of Tender of test certificates covering all specified tests deemed to be pertinent to the plant and to the conditions in which it will operate or, if such test certificates cannot be supplied or are deemed unacceptable by the Engineer, type tests which will be subject to the conditions of this Contract shall be carried out at no extra cost to the Employer.

The requirement for switchgear spares, tools and appliances, including test, maintenance and handling equipment shall be as stated in the tender document.

7.1.2 References

7.1.2.1 British Standards

BS 159 Specifications for HV bus bars and bus bar connections BS 1977 Specifications for high conductivity copper tubes for electrical

purposes BS BS

2898 3938

Specifications for wrought aluminium for electrical purposes. Strip with drawn or rolled edges. Specification for current transformers. BS 5253 Specifications for AC disconnectors and earthing switches.

BS 6651 Lightning Protection BS 7354 Code of practice for design of HV open terminal stations.

7.1.2.2 IEC Standards

1. IEC 62271 HV Switchgear and Controlgear. 2. IEC 60376 Specification and acceptance of new sulphur hexafluoride 3. IEC 60480 Guide to checking of sulphur hexafluoride taken from electrical

equipment. 4. IEC 60060 High Voltage test techniques. 5. IEC 60071 Insulation Co-ordination 6. IEC 60099-5 Surge arresters Part 5: Selection and application

reccommandation 7. IEC 60129 AC disconnectors (isolators) and earthing switches 8. IEC 60044-1 Current transformers. 9. IEC 60044-2 Voltage transformers. 10. IEC 60273 Characteristics of indoor and outdoor post insulators for

systems with nominal voltages greater than 1000V.

251

11. IEC 61850 Communication network and system in substation 12. IEC 60529 Degrees of protection provided by Enclosure (IP code) 13. IEC 60255 Electrical relays 14. IEC 62271-1 High voltage switchgear and control gear: common specification 15. IEC 62271-

100 High voltage switchgear and control gear: Part 100: Alternating current circuit breakers

16. IEC 62271-102

High voltage switchgear and control gear: Part 102: Alternating current disconnector and earthing switch

7.1.3 33 kV Vacuum Circuit Breaker

7.1.3.1 General Features:

1. Installation : Outdoor Sub-station.

2. Type : Vacuum Circuit Breakers

3. Number of Phase : 3 (Three)

4. Operation : Single Break in Service/ Pole

5. Service Voltage : 33 KV

6. Maximum Rate Voltage : 36 KV

7. Frequency : 50 Hz

8. Normal Rated Current for : 1250 A

9. Symmetrical Breaking Capacity : 1500 MVA

10. Asymmetry : 50%

11. Short Time Current Duration : 25 KA, 3 Sec.

12. Making Current (Peak) KA : 62.3KA

13. Opening Time (Maximum) : 0.05 Sec.

14. Breaking Time : 5 Cycle

15. Capacity of Vacuum Interrupter at rated short circuit current switching

: 100 nos. of operations

16. Basic Insulation Level (1.2/50 Micro Second Wave)

: 170 KV

17. Power Frequency Test Voltage (Dry) 70 KV at 50 Hz, 1 Min.

18. Rated Operating Sequence : 0-0.3 Sec – CO – 3 min – CO

19. Standard : Design, Manufacture, Testing, Installation and Performance shall be in accordance with the latest edition of applicable IEC–6056 & IEC-62271-100

20. FEATURES

- Circuit Breaker terminal connectors shall be suitable for ACSR Martin, Merlin, Gross Beak(636MCM).

- Grading terminal connector.

252

- All current carrying parts shall be made of copper or Copper- Aluminum Alloy - Externally visible circuit breaker position indicator. - Electrically remote controlled operating mechanism. - Shall be capable of the interrupting duties produced by the switching of

transformer magnetizing current and the switching of line charging current. Tests certificate demonstrating this ability of the circuit breakers shall be submitted with the offer.

- Circuit Breaker closing mechanism shall be 230 volt AC motor wound spring-operated type such that the closing speed is independent of the operator.

- Shall be two tripping coils and one closing coil. - Hand closing and tripping shall be done through manual levers. - Trip free mechanism as specified in IEC 60056-1 i.e. tripping is independent. - Local “Close” and “Trip” controller. - VCB should be re-strike free. - VCB should be trip free. - Operation Counter. - Supporting Steel Structure.

- Bushing Insulator as Specified in IEC-60137.

- Weather proof sheet steel control kiosk, with hinged door on three sides and necessary multi-core cable glands. Controls from this position will normally is used under maintenance and emergency conditions only. AC 230V lighting system inside the door of control kiosk shall be provided.

- ARC suppression type contacts. - Manually operating devices for slow closing for inspection and maintenance. It

shall not be possible to slow close a breaker when in normal services. - Earthing pad with provision for earth leads. - Standard sundries like anti-condensation heaters, MCBS wiring board etc. Facilities to be incorporate for tripping and lockout of the breaker in the event

Vacuum failure falling below stipulated value.

- Rating plate and diagram plate shall be made of stainless steel and have engraved letters filled with black enamel paint.

- Evidence of prototype tests together with test certificate from a recognized institution covering the equipment shall be furnished with the offer. The test duty shall be as per the requirements of IEC–60056.

- Laminated control & protection drawing set shall be fitted/supplied inside the control box/kiosk.

- Motor-driven, spring charged

- Automatically charged after each closing operation

- O-C-O operation without recharging

- Mechanical / electrical anti-pumping

- Provision for manual charging

- Manual closing and tripping arrangement

- Mechanical ON-OFF, operation counter and spring-charged indication

- All necessary positive interlocks installed, as per IEC guidelines.

253

7.1.3.2 TESTS AT MANUFACTURERS WORKS FOR OUTDOOR TYPE VCB

General

Functional electrical, material, mechanical and hydraulic tests shall be carried out at manufacturers’ premises. The extent and method of recording the results shall be agreed by the Purchaser in ample time to enable the tests to be satisfactorily witnessed or to make any changes to the proposed program of tests.

Material Tests

The supplier shall provide test pieces free of charge as required to enable the quality of the material to be determined at the supplier’s expense. Purchaser may at its own discretion and by specific arrangement accept certified particulars of tests carried out in the absence of his authorized representative. Type Test

Type tests are required to prove the general design of the offered equipments/ materials. The Tenderer shall submit the type test reports of the offered equipments/ materials from as per relevant clause.

Routine Tests

All equipments/ materials shall be subjected to routine tests as per latest version of relevant IEC/ BS or equivalent international standards as mentioned in the contract at the manufacturers works and shall include, but not be limited to, an operational test.

7.1.4. 33KV PCM

7.1.4.1 General

The panels shall be vermin and dust proof free standing type completely metal enclosed by

sheet steel (minimum 1.62 mm thick) with necessary reinforcement color gray with appropriate

spray painting. The approximate size will be high 2350 mm, width 700 mm and front 900 mm,

suitable for opening at the back by hinged door with locking arrangement. The panels shall be

neatly and completely wired before shipment.

The work relating to protection, control and panels for 33/11KV Sub-stations shall comprise of

development of elementary diagram, design, manufacture, test and supply of pre-wired control

panels to be installed in the sub-station control room. The protection, control and panels are to

be pre-wired with relays and meters in position. The elementary primary diagram shall be

produced giving a clear representation of each protection, control and metering function. The

standard design, drawing, manufacturing, testing & performance shall be in accordance to the

IEC-298 standards.

7.1.4.1. A. 33 kV Control, Metering and Relay Panel For Power Transformer , each

Panel comprising:

1. Indicating analogue Ampere meter 0-300/600A for 10/13MVA Transformer to

current transformer ratio 300-600/5-5-5A for 10/13 MVA Transformer.

3 (three)

nos.

2. Indicating analogue voltmeter with six position selector switch flush mounting

with scales 0-40 KV for connection to potential transformer ratio (33/3)/

(0.11/3)/(0.11/3) KV, (50 Hz).

1 (one)

set

254

3. Numerical Programmable Multifunction KWh Meter of class of accuracy 0.2 with

the features for measuring the parameters viz. phase voltages, phase currents,

system frequency, per phase & total KW with demand, KVAR, Power factor etc.

1 (one)

no.

4. Numerical programmable type Three Phase combined IDMT Over Current relay

and Earth fault protection relay of 5 Amps, 50 Hz, 110V dc, 3 second operating

time ratings having 3 (Three) over current units and one earth fault with current

setting of 50 to 200% and one earth fault unit with current setting 20 to 80%

suitable for operation from 5A current transformers. The relays are housed in a

horizontal, flush mounting draw-out case (tropicalized) with self-reset trip relay

(relaying 02 nos. NO contacts as spares) (Not to be included in Differential Relay).

1 (one)

set

5. Numerical programmable type Differential relay with REF inbuilt feature for

33/11KV, 10/13MVA Power Transformer. The relay(s) are housed in a horizontal,

flush mounting draw-out case (tropicalized) with hand-reset trip relay (having 02

nos. NO contacts as spares).

1 (one)

set

6. All necessary switches, CT, PT test terminal blocks, signaling set lamps, master trip

relay, trip circuit supervision relay for each trip coil, PT supervision relay, auxiliary

relay, MCB, fuse and provision for lighting etc. terminal blocks, mimic diagram with

circuit breaker control indicating switches and isolating position indicating

switches, indicating lamps shall be provided to indicate “Spring Charge”/ readiness

for closing and healthy trip circuit indicating readiness for tripping. The mimic and

positions of circuit breaker control cum position indicating switch and isolator

position indicating switch arrangement in the switchyard. There shall be 15

(fifteen) fault-signaling relays/windows in the annunciator, having inbuilt flashing

& horn features.

1 (one)

set

7. 100 W, 230 V AC, Single Phase heater with thermostat and a visible light indicator

which indicate the ''ON"- ''OFF" position of the heater

1 (one)

set

7.1.4.1.B 33 KV CONTROL, SIGNALING METERING AND RELAY PANEL FOR INCOMING /OUTGOING

FEEDER

1. Indicating analogue Ampere meter flush mounting with dual scales option (0-400A

& 0-800A any one may use) for connecting to the current transformer (ratio 800-

400/5-5A)

3 (three)

nos.

2. Indicating analogue voltmeter with six position selector switch flush mounting

with scales 0-40 KV for connection to potential transformer ratio (33/3)/

(0.11/3)/(0.11/3) KV, (50 Hz).

1 (one)

set

3. Numerical Programmable Multifunction bi-directional KWH energy meters with

export and import energy measuring features of class of accuracy 0.2 with the

features for measuring the parameters viz. phase voltages, phase currents, system

frequency, per phase & total KW with demand, KVar, Power factor etc.

1 (one)

no.

255

4. Numerical programmable type Three Phase combined IDMT Over Current relay

and Earth fault protection relay of 5 Amps, 50 Hz, 110V dc, 3 second operating time

ratings having 03 (Three) over current units and 01(one) earth fault with current

setting of 50 to 200% and one earth fault unit with current setting 20 to 80%

suitable for operation from 5A current transformers. The relays are housed in a

horizontal, flush mounting draw-out case (tropicalized) with self-reset trip relay

(relaying 02 nos. NO contacts as spares) (Directional Over Current and Directional

Earth Fault Scheme shall have to be incorporated separately in the above

mentioned Over Current relay and Earth fault protection relay).

1 (one)

set

5. All necessary switches, CT, PT test terminal blocks, signaling set lamps, master trip

relay, trip circuit supervision relay for each trip coil, PT supervision relay, auxiliary

relay, MCB, fuse and provision for lighting etc. terminal blocks, mimic diagram with

circuit breaker control indicating switches and isolating position indicating

switches, indicating lamps shall be provided to indicate “Spring Charge”/ readiness

for closing and healthy trip circuit indicating readiness for tripping. The mimic and

positions of circuit breaker control cum position indicating switch and isolator

position indicating switch arrangement in the switchyard. There shall be 8 (eight)

fault-signaling relays/windows in the annunciator, having inbuilt flashing & horn

features.

1 (one)

set

5. 100 W, 230 V AC, Single Phase heater with thermostat and a visible light indicator

which indicate the "ON"- "OFF" position of the heater

1 (one)

set

7.1.4.1.C FOR 33 KV PANEL FEATURES:

Each PCM panel shall be equipped with the following:

a.) Instruments and Relays described elsewhere.

b.) Status indicating discrepancy, Control switches for 33 kV Circuit Breaker with safety

arrangements.

c.) Illuminated Circuit Breaker and Isolator position switches.

d.) Signaling relays (compact type) to yield audiovisual signals on faults and have reset

feature.

e.) The inside of the panel will have all auxiliary relays to sense the operation of gas

relays, over temperature, over current, differential relay operation failure of

auxiliary voltage (DC & AC) etc. and to transmit for tripping and fault signaling.

f.) All inside equipment described and required shall be neatly arranged inside the

panel.

g.) Thermostat control heater with status indicating illumination lamp (CFL) shall be

provided.

h.) The terminal blocks for connecting the incoming multi-core cables shall be placed at

the bottom part and necessary glands/ opening shall be provided for the entry of the

outside cables.

i.) Sufficient-working spaces shall be provided inside the panel between instruments

and wiring for easy approach.

j.) All AC, DC auxiliary power circuits and PT secondary circuits entering the control

panel shall be provided with MCCB.

k.) Provision to hang danger/ caution board.

l.) Sufficient spare terminals (at least 10%) in each terminal block.

256

m.) Stabilizing resistance and Metrocil of appropriate value by calculation for the REF

scheme in PCM panel.

n.) Tripping from protection to circuit breakers shall be through Trip relays.

o.) CT, PT test terminal blocks and terminal blocks with isolation/shorting/jacking

feature(s) as applicable.

p.) Circuit Breaker control indicating switches and isolating position indicating lamps to

indicate spring Charge/ Readiness for closing and healthy trip circuit indicating

readiness for tripping.

q.) Signaling /indicating lamps shall be LED type only.

r.) Auxiliary relays, trip relays with spare contacts, fuses.

s.) All necessary switches etc.

t.) Provision for lighting etc.

u.) 100W, 230V AC, 1-phase heater with thermostat and control switch. and a visible

light indicator which indicate the "ON"- "OFF" position of the heater

v.) Mimic diagram. The color and size of the mimic shall be as described below :

33 KV GREEN ½'' X 1/8''

11 KV BLACK ½" X 1/8"

w.) Detailed schematic diagram of control circuit of PCM inside panel.

x) Separate relay shall be used for over current, Earth fault protection and differential

protection

xi) Annunciator window shall be 4X4 for incoming and outgoing panel and 4X6 for

transformer panel.

xii) Necessary communication cable and software shall be supplied.

7.1.4.1.D Alarms

The following alarm provision shall be made:

1. 33 KV TRANSFORMER FEEDER

a) DC Protection Supply Failure

b) Instantaneous Trip

c) IDMT Over Current & Earth Fault operated.

d) Differential / REF Protection operated.

e) Buchholz Alarm &Trip

f) PRD trip.

g) Tap Changer Oil Surge

h) Low Oil Level

i) Winding Temperature 1st stage and 2nd stage (alarm and trip)

j) Oil Temperature 1st stage and 2nd stage(alarm and trip)

k) AC supplies failure.

l) TCS-1 failure.

m) TCS-2 failure

n) PT supply failure.

2. 33 kV Incoming/Outgoing Feeder

a) DC Protection Supply Failure

b) Instantaneous Trip

c) IDMT Over Current operated.

d) Earth fault operated.

e) TCS-1 failure.

257

f) TCS-2 failure

g) PT supply failure.

Besides the provisions of control, signal, protection and metering described, any other

provisions to suit with the requirement of associated equipment of the concern feeder

shall be provided. All meters and relays shall be flush mounting. There shall be panel-

grounding terminal.

The bidder shall quote the particulars of various protective relays, meters, Auxiliary

relays signaling relays, discrepancy control and position indicating switches etc. of the

control panel, mentioning the names of the manufacturers.

7.1.4.1.E. TESTS

Complete tests shall be made at the manufacturer’s factory in accordance with the latest

relevant IEC 62271-200:2003 standards. Among others, at least the following test shall

be included:

a) Wiring Check

b) Functional check

c) Di-electric Test

d) Verification of protection

Test plugs shall be supplied. Test results of instruments and relays are to be

provided along with the bid.

7.1.4,1.F. Construction Details

Each panel shall be fabricated from steel sheet (minimum 1.62 mm thick) with

necessary steel member reinforcement to make the structure self supporting. All joints

are to be welded and ground to be made smooth.

Mounting brackets required shall be arranged inside the panel for mounting and fixing

auxiliary devices and terminal blocks.

Instruments meters control switches and protective relays shall be mounted on the

front panel only. Panel output mounting studs and support brackets shall be accurately

located.

Finished panel surface shall be free of waves and other imperfections exterior panel

surfaces shall be send blasted, ground smooth, filled, panel and finished with gray

enamel. Interior surface shall be sand blasted, primed and finished with glass white

enamel.

The panel shall be designed to have bottom closed and with an adequate number of 50

mm knock outs provided to facilitate entry of control wires and cables. The back end

closure of the panel shall be equipped with hinged formed door. The door shall be rigid

and shall be equipped with three point latches.

The supplier shall furnish internal panel wiring and circuit protection. The supplier shall

provide one 100W, 240, AC strip heater in the panel. The heater shall have a separate

switch. Engraved name plate shall be provided at the top of the front enclosure.

258

7.1..4.1.G.PANEL WIRING

The supplier shall provide internal wiring and connections, in accordance with the

requirements of the following paragraph.

All wiring used within the panel shall conform to the requirements of these

specifications and shall be installed and tested at the factory. All wiring shall be neatly

and carefully installed in wring gutters of raceway wiring raceway shall be plastic wiring

duct with covers. Instrument wiring on the panel shall be numbered sequentially from

the sources to the panel instrument and the number of the source equipment shall be

used as a prefix for the individual wire numbers, wiring shall be terminated at terminal

blocks plainly lettered or marked in accordance with the manufacturer’s connection

diagrams.

Sufficient clearance shall be provided for all the leads. All the leads for external circuit

wiring shall be connected to grounded terminal blocks located for convenient

connection of external circuits.

Splices will not be permitted in panel wiring.

All the terminal block connections shall be made with ring type lugs. Pre-insulated ring

type terminals with crimp guide or per-insulated slotted spring spade terminals shall be

provided on devices equipped with individual fitted covers.

Arrangement of circuits on terminal block shall be such that all the connections for one

circuit, plus any spare conductors, shall have terminal blocks adjacent to the split and

shall be provided with wiring required to interconnect the split unit.

The size of the wiring used in the panel shall be conform to the following requirements:

a.) Ampere meter and current transformer/ potential transformer circuit: 6 Sq.mm

(RYB color code shall be used)

b.) All other wiring: 2.5 Sq.mm.

7.4.1.1.H. POWER SUPPLY DISCONNECT

Each panel mounted devices requiring AC or DC supply, shall have disconnecting devices

from the power supply in the tripped or open condition.

The MCCB's used in DC control circuit shall have a rating of 6 A and 250 V. The tumbler

switch in the heater shall have the same rating.

Each S/S will be equipped generally with the following :

3 (Three) phase MCCB for incoming from Auxiliary transformers - 1 (one) no.

MCCB for incoming DC for battery - 1 (one) no.

MCCB for AC outgoing - 10 (ten) nos.

MCCB for DC outgoing - 10 (ten) nos.

The fuses shall be modular type with Bakelite frame and reinforced retaining clips.

7.1.4.1.J. INDICATING LIGHTS

Indicating lights of LED type shall be have transparent glass lenses and appropriately

sized resister.

7.1.4.1.K. TERMINAL BLOCKS

Terminal blocks shall provided with white marking strips, circuit designation by the

supplier shall be inscribed on the marking strip with black print, terminals in a quantity

259

of not less than 25 percent of the interconnected terminals in excess shall be provided

on each terminal block for circuit modifications and for termination of all conductors in

multi-conductor cable.

CT/PT terminal block shall have shorting, Isolation & Jacking facility.

CT, PT, Control, Alarm etc. wiring shall be separately grouped or segregated.

Terminal block shall be grouped in each panel for easy accessibility unrestricted by

interference from structural members and instruments. Sufficient spaces shall be

provided on each side of each terminal block to allow an orderly arrangement of all the

lead to be terminated on the block.

7.1.4.1.L. INSTRUMENTS AND DEVICES

Indicating instruments shall be semi flush panel type with 1% percent accuracy class

except for energy meters which shall be of 0.2. They shall be approximately 100 mm

square with black 250 degree scales on a white back ground.

All AC instruments shall be designed for operation on 5A current transformers

secondary and 110V (50 Hz) potential transformer secondary.

7.1.4.1.M. TRIP RELAYS Following shall be the main features of a high speed tripping relays:

All tripping relays shall be of the heavy duty type suitable for panel mounting and shall have

operating coils which are rated sufficiently to operate in conjunction with series flag relays. If

necessary, normally closed contacts in series with the relay operating coil, shall be delayed for a

period which will allow series flag relays to operate satisfactorily. All other tripping contacts

should be instantaneous i.e. no intentional time delay. The operating time shall not exceed 10

milliseconds at rated voltage. The operating range of the relay shall be from 70% to 120% of

rated voltage. Electrical reset facilities shall be available for operation, from remote and

supervisory controls. High speed tripping relays shall prevent closing of the associated circuit

breakers until reset. Wherever the tripping relay contacts need to break the d.c. current,

sufficiently rated magnetic blow out contacts or such approved means shall be used.

7.1.4.1.N. SUPERVISION RELAYS 7.1.4.1.N.1 Trip Circuit and Protection Supply Supervision

The trip circuit supervision function shall be part of control and protection unit provided in the

switchgear. Trip circuit supervision relays shall be provided to monitor each of the trip circuits

of all 11kV circuit breakers and each relay shall have sufficient contacts for visual/audible

alarm and indication purposes. The trip circuit supervision scheme shall provide continuous

supervision of the trip circuits of the circuit breaker in either the open or closed position and

independent of local or remote selection at the local operating position. Relay elements shall be

delayed on drop-off to prevent false alarms during faults on dc wiring on adjacent circuits, or

due to operation of a trip relay contact. Series resistances shall be provided in trip supervision

circuits to prevent mal tripping

a circuit breaker if a relay element is short circuited. Relay alarm elements shall be equipped

with hand resetting flag indicators.

260

7.1.4.1.N.2 D.C. Supply Supervision

Supervision relays are required for each protection supply, Main protection, Back-up and Trip

Relay Reset. Similarly for each trip circuit supply and for each alarm/ indications supply. These

supervision relays are to be independent of alarms from the trip circuit supervision scheme so

that the operator can clearly differentiate via the available alarms between loss of supply due to

a blown fuse / tripped MCB and failure of a trip circuits supervision /faulty supervision wiring.

261

7.1.4.1.O SPECIFICATION OF 110V, 3 x 5(6) A, 3-PHASE, 4-WIRE, 3-ELEMENT, INDOOR

TYPE MULTI-TARIFF PROGRAMMABLE METER WITH ASSOCIATED INSTRUMENT

TRANSFORMERS ENCLOSED IN METERING PANEL .

7.1.4.1.O.A GENERAL

The meters are required for the purpose of energy metering of medium/high/extra-high

voltage consumer metering at 132 kV or 33 kV or 11kV level . KWh is the unit for the

purpose.

System voltage Nominal service voltage 110V (PT Secondary),

3 phase 4wire, solidly grounded neutral at

source, maximum system voltage 120V line to

line.

System

frequency

50 Hz

7.1.4.1.O.B SPECIFICATION OF 110V 3 x 5(6)A, 3-PHASE, 4-WIRE 3-ELEMENT, INDOOR

TYPE MULTI TARIFF PROGRAMMABLE DIGITAL ENERGY METER

The consumer meters are required for the purpose of energy metering of low voltage

consumer who purchases power at 11 kV/33 kV line through PT & CT. kWh is the

unit for revenue purpose.

System voltage : Nominal service voltage 110V, 3 phase 4 wire, solidly grounded

neutral at source, maximum system voltage 120V line to line.

System frequency : 50 Hz

Standard : The Energy Meter should be designed, manufactured and tested in

accordance with IEC 62052-11, 62053-22 and 62053-23 or ANSI C

12.16, 12.10 (latest publication) or specified in this specification

Installation : Indoor Type

Type : Solid state.

Application : Registration of KWh (Peak & off-peak), Total KVarh(Q1+Q4), KW on

3- phase, 4-wire supply for balanced & unbalanced load

(unidirectional). Peak 17.00-23.00. hrs and off peak 23.00-17.00 hrs

(programmable) Bangladesh standard time. The software for Time of

Use (TOU) shall be so developed to accommodate future tariff and

can be customized, if the purchaser changes the tariff. The software

shall be compatible with Windows operating system.

Connection : 3-phase 4-wire, solidly grounded neutral.

Nos. of element : 3 (Three)

Rated current : Basic current 5 amps and maximum current 6 amps.

Multiplication factor : The following shall be inscribe on the mater. Dial reading X CT ratio X

PT ratio = Actual reading in KWh.

Register : Solid state LCD display type register. The display shall be

programmable, automatic and include:

Meter ID

Time & date

Cumulative KWh (Peak & off-peak)

Cumulative Total KVarh (Q1+Q4)

262

Maximum demand (KW) with time & date

Cumulative Maximum demand (kW) for billing month.

Maximum demand (MD) in kW shall be registered using the

technique of cumulating on integration period controlled by built-in

process and the MD shall be continuously recorded and the highest

shall be indicated. The highest MD shall be added to the cumulative

store, which shall be automatically initiated after an interval of one

month / one billing period by means of built-in timing device.

Integration period: 30 (thirty) minutes.

Number of MD reset (Automatic& manually).

Average PF for billing period.

Instantaneous:

Phase voltage with indication

Phase amps with direction.

Power factor (average).

Demand (KW)

Voltage phase angel (each phase)

Current phase angle(each phase)

Tampering indication in the register.

Memory storage : The meter shall have sufficient capacity (minimum 400 KB) to store

the following readings and data in non-volatile memory even in case

of power failure.

Equipment identification codes, security codes and access codes.

Number of power interruption with date & time (minimum 100

events).

Latest power failure time & date

Date & time of meter tempering. (Voltage & Current missing,

demand reset , time change).

Event logs

Current & Previous registered in month KWh (Peak & off-peak),

Total KVarh (Q1+Q4)

Current & Previous month registered with maximum KW demand

since last MD reset with time and date of its occurrence.

The meter must have sufficient capacity to store data at 30 (thirty)

minutes interval for at least 90 (ninety) days.

Load Profile data [kWh, KVarh (Q1+Q4)

Phase voltage or Vh

Phase amps or Ah

Accuracy class : Accuracy class is 0.2 (point two)

Number of digit Minimum 5 (Five) integer with 1 (One) decimal (Total 6 digit).

Type of Display Solid-state LCD display.

or P.F. Angle(each phase)

263

Time switch : The time switch shall be built-in type and shall be designed to

perform a present cycle of operation. Time switch shall reset MDI at

the end of every month (billing period) automatically. In the event of

failure of power supply and battery, at the same time set memory

shall not be lost i.e. the set program shall be recorded in non-volatile

memory. The maximum error shall be kept within 1 (one) second

per day. Time error adjustment facility shall be provided.

Battery reserve : Each time switch must be provided with lithium battery which allow

the switch to function for a period of not less than 10 (ten) years. The

guaranteed life of the battery should not be less than 10 (ten) years

and shall have provision for easy replacement. The shelf life of the

battery should be minimum 15(fifteen) years or more.

Construction : The meter shall be completely self-contain round socket or enclosure

type. The meter cover shall be made of polycarbonate/acrylic

/phenolic /resin and socket cover shall be made of metal

polycarbonate/ acrylic /phenolic /resin. The meter cover and socket

/enclosure shall be provided with security sealing provisions to

prevent unauthorized access to the internal meter works and socket

/enclosure sealing shall be designed to accommodate both padlock

and wire type seal.

IEC meters shall be minimum IP51. The ANSI Standard meter shall be

effectively sealed to prevent entrance of rain and dust into its

internal parts. The meter shall pass Rain test described in

underwriter’s laboratory standard UL-50 (USA) for type 3 enclosures.

A general purpose finish of class 1 as specified in section 7 of ANSI

C12.10 shall be provided for the meter and it shall meet the

requirement of weather simulation test (Sec. 7.2.1 of ANSI C12.10)

and salt spray test (ASTM B117). It shall be designed to operate

continuously for the normal life of the meter in unsheltered outdoor

tropical location exposed to the elements without corrosion or other

damage to parts to adversely affect meter accuracy or reliability.

Enclosure for IEC

Standard Meter

The meter shall be surface mounted in an outdoor pole mounted

metering enclosure box with necessary wiring. The enclosure box

should be made either of high quality flame retardant ABS Resin of

minimum 3 mm thickness or of galvanized sheet steel of minimum

1.22 mm (18 SWG) thickness or of auto extinguishable, shockproof

and UV resistant, hot molded glass reinforced polyester of minimum

3 mm thickness. The box shall have hinged front door with one

toughened glass window or transparent UV resistant Polly carbonate

to enable easy reading of meter. The metering box shall be weather

proof, dust proof, rodent and inspect proof in accordance with

enclosure classification IP54. Service cable entry and exit will be

sides of the box and 40 (forty) mm diameter hole with black PVC

conic cable gland shall be provided for side entry & exit for this

purpose. All material parts shall have anti-corrosive protection.

264

All materials shall be designed, manufactured and tested as per IEC

or equivalent International standards except as mentioned. The front

door shall be removable and provision must be made for sealing in

the closed position.

Socket : Meter sockets shall be suitable for installation of offered type meter.

Meter sockets shall be 3-phase, 4-wire wye, 600 volt class,

made from 16 gauge sheet metal. Meter sockets shall be similar

except as described below. Meter sockets shall approximately

14 (35.6 cm) H9(22.9cm) W4 (10.2 cm) D and rectangular

in shape. Sockets shall be the same size as 1-phase sockets and

terminal blocks shall be interchangeable. Sockets shall be ring

less type, sealing latch to be stainless steel and have adequate

means for socket grounding. Meter socket shall have a 2(5 cm)

Diameter top opening complete with a 1- ¼ (3.2 cm) hub.

Meter socket shall have 4 knockouts with a range up to 2(5

cm) Diameter, one on the back, one in the bottom and one in

each side. Meter socket shall comply with ANSI C 12.6, 12.10

The Socket shall have written permanently (not in paper

printed) “connection diagram” distinctly marked in addition to

all standard

data.

Terminal : Socket connected type/ Non-symmetrical, bottom entry, front

connection, and connection type with extended terminal cover:

Minimum 10 Terminals to accommodate up to 06 sq. mm size of

cable. The terminal cover for the offered energy meter shall be

extended type, and which can be sealed independently. There shall be

free space between bottom of the terminal and the bottom of the

terminal cover.

Connection

: 3-phase, 4-wire solidly grounded neutral.

Service life of meter : Shall be minimum 15 (fifteen) years.

Visual indication of

operation

: Pulse indicator on the front of meter as per meter constant.

Special condition : a) The factory calibration conforms to

relevant IEC or equivalent international

standard. LCD display shall be shown

consecutively and continuously one after

another. The display shall be automated

i.e. no external means shall be required to

see the display. Each display shall last for

at least 5 (five) sec.

265

b) Meter Electronic Circuit biasing voltage

shall have to be ensured from each phase

to phase and each phase to neutral and

minimum basing voltage 40V.

Meter Sealing : The Energy meter body will be hermetically sealed or ultrasonically

welded to avoid unauthorized opening of meter cover. Otherwise the

bid will be rejected.

Communication port : The meter must be provided with a suitable communication port to

allow down loading of desired information stored in the meter to a

PC via hand held data logger as per IEC 1107 or equivalent standard.

Remote Communication : The meter shall be equipped with external GSM-GPRS Modem, which

will be able to interface with RS232, RS485 for data communication

with the central server from meters, having all accessories like power

supply adapter, necessary connecting cables, antenna with minimum

2.5 meter extension cable, connectors, enclosure box with fixing

materials etc. The modem shall be compatible with existing AMR

system of BPDB.

7.1.4.1.O.C. TAMPER AND FRAUD PROTECTION FEATURE:

The meter shall have the following features to prevent/detect tamper and fraud:

Phase Sequence Reversal: The meter should work accurately irrespective of

phase sequence of supply.

Missing Potentials: The meter shall be capable of detection occurrence of

missing potential of one phase or two phase(s), which can happen due to

intentional/accidental disconnection of potential link(s).

Terminal cover must have micro-switch provision to monitor unauthorized

opening. Opening of terminal cover shall trigger an event to be recorded in the

event log memory.

Software Access: Software access for configuration and setting of the meters.

7.1.4.1.O.D TECHNICAL FEATURE

The body cover and socket / enclosure shall be provided security sealing

provisions to prevent unauthorized access to the internal meter works.

The meter shall be provided with connection diagram.

The data access should be protected by minimum 3(three) steps software

password in meter.

The meter shall have provision of phase to phase and each phase to neutral

biasing.

The meter shall have minimum biasing voltage of 40V otherwise the bid will

be rejected.

The meter and socket/enclosure shall have provision of earthing.

266

Meter must operate and accurately register demand and energy when

service voltage is applied across any two of the three input terminals or

when service voltage is applied from any input terminal to neutral. Meter

will continue to operate even the neutral is missing.

The meter and socket/ enclosure must be the same country of origin other

wise the bid will be rejected.

The registration of KWh (Peak & off-peak) on 3-phase, 4-wire supply for

balanced & unbalanced load will be unidirectional. i.e. if one, two or three

phase supply is/are reversed, it will take the absolute (kWh-del) + absolute

(kWh-rev) and will add them together as total 3-phase KWh.

The meter shall be equipped with remote GSM & PSTN communication

option.

The meter shall have permanently print nameplate distinctly marked with

the following in addition to all standard data:

1. The word “BPDB” and insignia of BPDB.

2. Voltage and current rating.

3. Frequency.

4. Number of element, number of wire and multiplication factor.

5. Accuracy class.

6. Year of manufacture.

7. Serial number.

8. Name of manufacturer.

9. Meter constant.

7.1.4.1.O.E. Display of measured values/ Meter Display

The Sequence of LCD display should be user programmable.

The contrast setting of LCD display should be visible in different lighting

environment and distinctly visible in broad daylight.

The meter should be of displaying time and date, the direction of energy

i.e. as import/export or +/-, active tariff and internal fault indicators.

There should be up to three groups of display to priorities the display.

Each showing a programmable function group.

7.1.4.1.O.F Meter Parameterisation Software

The parameterisation software must run on Windows operating

environment.

The software must be protected by software keys to control duplication and

installation.

The software should have a customizable printing feature by task list.

The meter must be able to display or record meter ID, Program,

Programmer ID, C. T. ratio, V. T. ratio, Total (KWh, KVarh, KVAh, KW, KVar,

KVA, P.F); per phase ( voltage, current, KW, KVar, KVA, P.F, phase voltage

angle, phase current angel); Load profile having minimum 8(eight) Channels

data stored in different interval for 90 days.

267

Tamper feature: The meter must have Errors & Warnings codes, History log

and Event log(minimum 400events) to record date & time of all power

outages, demand resets, time change.

In addition, each software key must bear a unique user ID and that is not

transferable to another PC that has different user ID.

The Meter should be able to display the phasor diagram.

The software for Time of Use (TOU) shall be compatible to accommodate

future tariff and can be customized, if the purchaser changes the tariff .The

software shall be compatible with Windows operating system.

The Meter must be provided with meter passwords to secure

communication between meter software and meter having minimum

3(three) access levels.

The AMR Software have to be compatible with BPDB’s existing AMR System.

The Tenderer have to develop the total AMR System with exiting and

supplied AMR Solution. In this case the tenderer have to provide their meter

protocols so that all exiting meters and supplied meters data will be

downloaded and managed in a single AMR System.

7.1.4.1.O.G EXTERNAL MODEM WITH ACCESSORIES

GSM/GPRS modem with RS-232 ports, meter interfaced power supply, connection

cables, antenna with minimum 2.5 meters cable, mounting facilities, enclosure (if

necessary). The modems will be capable of GSM and GPRS connectivity simultaneously.

For GSm configuration the AT command will be available and for GPRS communication

the APN, reset time, username, password, port number, etc. are configurable. The

modem will have the following specification.

Interruption (< 1 ms), RS-232 (at least 1), GPRS class 10, operating band 900/1800, auto

reset capability (with phone call, SMS). The modem will be robust, durable and

compatible with the employers existing service condition.

7.1.4.1.O.H Manufacturer

All the energy meter shall be supplied from any of the following manufacturers:

a) Siemens, Germany/Switzerland.

b) AEG, Germany.

c) ABB, Switzerland/Finland

d) Toshiba , Japan

e) Elster, USA/Romania

f) Landis+ gyr , Switzerland/ Greece.

g) Honeywell , USA

Note: Related software & accessories if required for Energymeters is within the

scope of supply.

268

7.1.4.1.P. PROTECTIVE RELAYS

All Protective relays & Auxiliary relays shall be numerical programmable type and shall

comply relevant IEC or equivalent international standard. Contract arrangement of the

relays should conform to the requirements of the diagram.

All the protective relays shall be supplied from any of following manufacturers:

ABB (Switzerland/Finland/Sweden)/Siemens (Germany)/ Alstom (france/UK)/

Schneider (france/UK)/ NR, China.

Note: Related software & accessories if required for Energymeters is within the scope of

supply.

7.1.4.1.Q. AUXILIARY RELAY & TRIP RELAY

Trip Relay shall be provided for the tripping of CB by protection. Each 33KV PCM Cubicle

will be provided with 1 (one) set separate Auxiliary and signaling relays and wiring with

fuses.

7.1.4.1.R. ANNUNCIATOR

Each 33 kV PCM Cubicle will be provided with 01 (one) set separate Annunciator and

signaling relays and wiring with fuses, 02 nos. windows shall be kept spare.

7.1.4.1.S. INDICATING AMMETERS

Each 33 KV PCM Cubicle will be provided with 3 Ammeters (1 for each phase), analogue

type.

7.1.4.1.T . INDICATING VOLTMETERS

1 (one) voltmeter with a multi-selector switch (phase to phase, phase to neutral, off)

shall be installed on 33 KV transformer panel.

7.1.4.1.U. MIMIC BUS

Mimic bus material shall be brass, bronze or copper with enamel finished or anodized

aluminum or plastic. The mimic bus and included symbols shall be shaped, colored

and located as international standard. Light indicator showing position

(opening/closing) of circuit breaker shall be installed.

The mimic bus shall be attached to the panel by mechanical devices, not with adhesive.

Attachment shall be closely spaced to hold all parts of the mimic bus firmly to the panel

face.

Mimic bus shall be provided with the following dimensions and color code:

Voltage Bus Color Thick Dimension (mm)

33 KV Green 3 12

Note : One set of relay testing plug shall be supplied with protection, metering and

control panel which will be included in the quoted price. Each cubicle shall be complete

according to the specification, features and bill of materials but not limited to

these items; the cubicles should be complete in all respects, to make it fully

operational.

7.1.5 TECHNICAL SPECIFICATIONS 11KV VACUUM CIRCUIT BREAKERS WITH

PROTECTION, CONTROL & METERING CUBICLES.

269

7.1.5.1. . GENERAL

One panel structure and enclosure assembly with supports, Busbar compartments, Circuit breaker compartment, LV compartment, V.T Compartment, Cable termination compartment, earthing, Mechanical operating/ Indicating devices, Interlocks, LV compartments with all wiring MCBs, Fuses,Links, Auxilary relays, Supervision relays, Heater, Humidistat, Indications lamp, control and selector switches, Local and remote switches, Interlocking facilities, Voltmeter with selector switches, Terminal blocks, CTs/ VTs etc. as required for the complete unit for control and protection HV side requirement etc. The panel shall be suitable for connecting to 20/26.67 MVA power Transformer in accordance with the drawing.

1. Installation Indoor

2. Type Vacuum, Draw-out Pattern Cubicle

3. Bus-bar Scheme Single bus bar

4. Construction The structure of the cell is made of special sheet clad with convenient treatment which in all respect resists the effected of indoor humid tropicalized climate.

5. Mounting Floor Mounting/ Trolley Type

6. System 3-Phase, 3-Wire with earthed Neutral

7. Nominal System Voltage 11 kV Phase to Phase

8. System Highest Voltage 12 kV Phase to Phase

9. Rated short duration power frequency withstand voltage

28 kV (rms)

10. Rated Lightning Impulse withstand voltage 75 kV (peak)

11. Frequency 50 Hz

12. Rated normal current:

a) for 10/13 MVA Power Transformer 11kV Incoming & Bus Coupler

1250A

b) for 11KV outgoing feeder 630A

13. Temperature rise of any part of the switchgear & control gear

Shall be as per the latest revision of relevant IEC standards.

14. Rated Short-time withstand Current (Rated short circuit breaking current)

Min 25 KA for 3 Sec.

15. Rated Peak withstand Current (Rated short circuit making current)

Min 63 KA

17. Opening Time ≤ 0.05 Sec.

18. Breaking Time ≤ 5 Cycle

19. Rated supply voltage of closing & opening devices and auxiliary circuits.

110 Vdc & 240/415 Vac.

20. Rated supply frequency of closing & opening devices and auxiliary circuits.

DC & 50Hz.

21. Rated Operating Sequence 0-0.3sec-CO-3Min-CO

22. Degrees of Protection by enclosures (IP) IP4X as defined in IEC 60529

270

23. All Current Carrying Parts of VCB Shall be made of copper.

24. Dimensions of all 11kV Cubicles (including bus bar height and size)

Shall be matched in all respect.

25. Standard Design, Manufacture, Testing and Performance shall be in accordance to the IEC-62271-200 and other related IEC standards.

7.1.5.2. 11KV TRANSFORMER INCOMING CUBICLES, EACH COMPRISING:

1. Type of Bus Bar HDHC copper 1250 A. 2. Bus Bar Scheme Single Bus Bar 3. Type of Circuit Breaker Vacuum 4. Number of Phases 3 (Three) 5. Operating Mechanism For Circuit Breaker operation, both spring-

operated and stored-energy mechanisms shall be available. With manual Power/ Manual, Trip Free, Electrically Spring wound operated by 240 Vac and shunt trip by 110 Vdc from storage battery, vertically disconnected horizontal draw-out type with 2 Nos. Trip coils. The operating sequence OPEN- CLOSE-OPEN is stored in the springs.

6. Rupturing Capacity. 500 MVA, Symmetrical. 7. Breaking Time. 5 Cycle Maximum 8. Continuous Current Rating. 1250 Amps. 9. All Current Carrying Parts of VCB. Shall be made of Copper 10. AC Control Voltage 240 10% Volts 11. DC Control Voltage. 110 10% Volts 12. Cable and Boxes for Incoming. Suitable for size 1x2Cx240 mm2 XLPE 11kV

cables with copper conductors.

13.

Single Phase Current Transformer with Ratio 600-1200/5-5A for 10/13.33MVA power transformer of burden & accuracy class-30VA & 0.2 (for measurement) and 30VA & 5P20 (for protection). (Characteristics: Epoxy resins insulated and double windings, butyl rubber type. The epoxy resin should be ultraviolet stabilized, fungus resistant & high tracking resistance, short time current ratings 25KA for 3 second & extended current ratings 120% of the rated value, secondary double winding, installation shall be in the panel).

3 Nos. (A Phase, B Phase & C Phase Shall have

Indidual CT)

14.

Numerical, programmable IDMT & Instantaneous type Over Current and Earth fault protection relay with Standby Earth fault and all other necessary features for transformer incoming feeder protection.

1 set

15. Master Trip & Trip Circuit Supervision relays. 1 Set 16. All necessary Auxiliary & Signaling relays. As required.

271

17.

Numerical Programmable Multifunction 3-phase, 4-wire KWH Meter of accuracy class 0.2 with the features for measuring the parameters viz. phase voltages, phase currents, per phase & total KW with maximum demand, KVar, Power factor etc.

1 No.

18. AC Analogue Ammeter, 0-900/1800 A 3 Nos.

19. 100W, 240V AC, Single Phase space heater with thermostat and a visible light indicator which indicate the "ON"- "OFF" position of the heater

1 set

20.

All necessary AC DC MCB, TNC Switch, Selector Switch, Limit Switch, Control Switch, Toggle Switch, Link/ Base, Push Button, Indicating/ Illumination Lamp, AC Plug Socket, Wiring, Fuses, Hooter etc. i.e. complete in all respect.

As required.

21.

Alarms

a) DC Supply Failure b) Over Current Trip c) Earth Fault Trip d) Standby Earth Fault Trip e) TSC-1 failure f) TSC-2 failure g) MCCB failure etc

22. 11kV PT As described in Clause 7.08 may also be proposed.

7.1.5.3 . BUS COUPLER WITH BUS RISER CUBICLES EACH COMPRISING:

1. Type of Bus Bar HDHC copper 1250 A.

2. Bus Bar Scheme Single Bus Bar

3. Type of Circuit Breaker Vacuum

4. Number of Phases 3 (Three)

5. Operating Mechanism For Circuit Breaker operation, both spring-operated and stored-energy mechanisms shall be available. With manual Power/ Manual, Trip Free, Electrically Spring wound operated by 240 Vac and shunt trip by 110 Vdc from storage battery, vertically disconnected horizontal draw-out type with 2 Nos. Trip coils. The operating sequence OPEN- CLOSE-OPEN is stored in the springs.

6. Rupturing Capacity 500 MVA, Symmetrical

7. Breaking Time 5 Cycle Maximum

8. Continuous Current Rating 1250 A

9. All Current Carrying Parts of VCB Shall be made of Copper

10. AC Control Voltage 240 10% Volts

11. DC Control Voltage 110 10% Volts

12. Voltage Selection Relay 1 No.

272

13. Single Phase Current Transformer with Ratio 600-

1200/5-5A for 10/13.33 MVA power transformer of burden & accuracy class-30VA & 0.2 (for measurement) and 30VA & 5P20 (for protection).

(Characteristics: Epoxy resins insulated and double windings, butyl rubber type. The epoxy resin should be ultraviolet stabilized, fungus resistant & high tracking resistance, short time current ratings 25KA for 3 sec. & extended current ratings 120% of the rated value, secondary double winding, installation shall be in the panel).

3 Nos.

(A Phase, B Phase & C Phase Shall have Indidual CT)

14. Numerical programmable type Over Current and Earth fault protection relay with all necessary features for Bus Coupler protection.

1 set

15. Master Trip & Trip Circuit Supervision relays. 1 Set

16. All necessary Auxiliary & Signaling relays. As required.

17. 100W, 230V AC, Single Phase heater with thermostat and a visible light indicator which indicate the "ON"- "OFF" position of the heater

1 set

18. All necessary AC DC MCB, TNC Switch, Selector Switch, Limit Switch, Control Switch, Toggle Switch, Link/ Base, Push Button, Indicating/ Illumination Lamp, AC Plug Socket, Wiring, Fuses, Hooter etc. i.e. complete in all respect.

As required.

19.

Alarms

a) DC Supply Failure b) Over Current Trip c) Earth Fault Trip d) Standby Earth Fault Trip e) TSC-1 failure f) TSC-2 failure g) MCCB failure etc

7.1.5 .4. OUT-GOING CUBICLES, EACH COMPRISING:

1. Type of Bus Bar HDHC Copper 1600A. 2. Bus Bar Scheme Single Bus Bar 3. Type of Circuit Breaker Vacuum 4. Number of Phases 3 (Three) 5. Operating Mechanism For Circuit Breaker operation, both spring-operated

and stored-energy mechanisms shall be available. With manual Power/ Manual, Trip Free, Electrically Spring wound operated by 240 Vac and shunt trip by 110 Vdc from storage battery, vertically disconnected horizontal draw-out type with 2 Nos. Trip coils. The operating sequence OPEN- CLOSE-OPEN is stored in the springs.

6. Rupturing Capacity 500 MVA, Symmetrical. 7. Breaking Time 5 Cycle Maximum 8. Continuous Current Rating 630 Amps 9. Cable and Boxes for Incoming Cable Suitable for size 1x3Cx185 mm2 or 500 mm2 11 KV

XLPE cable with copper conductors. 10. AC Control Voltage 240 10% Volts 11. DC Control Voltage 110 10% Volts

273

12. All Current Carrying Parts of VCB Shall be made of Copper 13. Single Phase Current Transformer of Ratio 200-

400/5/5A of burden & accuracy class-30VA & 0.2 (for measurement) and 30VA & 5P20 (for protection). (Characteristics: Epoxy resins insulated and double windings, butyl rubber type. The epoxy resin should be ultraviolet stabilized, fungus resistant & high tracking resistance, short time current ratings 25KA for 3 sec. & extended current ratings 120% of the rated value, secondary double winding, installation shall be in the panel)

3 Nos. (A Phase, B Phase & C Phase Shall have Indidual

CT)

14. Numerical programmable type Over Current and Earth fault protection relay with all necessary features for 11KV Outgoing feeder protection.

1 set

15. Master Trip & Trip Circuit Supervision relays. 1 Set 16. All necessary Auxiliary & Signaling relays. As required. 17. Numerical Programmable Multifunction 3-phase, 4-wire

KWh Meter of accuracy class 0.2 with the features for measuring the parameters viz. phase voltages, phase currents, per phase & total KW with maximum demand, KVar, Power factor etc.

1 No.

19. AC Analogue Ammeter, 0-200/400 3 Nos. 20. 100W, 230V AC, Single Phase heater with thermostat

and a visible light indicator which indicate the "ON"- "OFF" position of the heater

1 set

21. All necessary AC DC MCB, TNC Switch, Selector Switch, Limit Switch, Control Switch, Toggle Switch, Link/ Base, Push Button, Indicating/ Illumination Lamp, AC Plug Socket, Wiring, Fuses, Hooter etc. i.e. complete in all respect.

As required.

22.

Alarms

a) DC Supply Failure b) Over Current Trip c) Earth Fault Trip d) Standby Earth Fault Trip e) TSC-1 failure f) TSC-2 failure g) MCCB failure etc

7.1.5.5 MEASURING CUBICLES, EACH COMPRISING:

a) 3 nos. epoxy resin-insulated single phase potential transformer having a ratio of

(11/3)/0.11/3)/0.11/3) kV (50 Hz), accuracy class 0.2 for measurement and 3P for protection,

rated burden of 30VA connected to the bus through fuses. The epoxy resin should be ultraviolet

stabilized, fungus resistant and should have high tracking resistance.

b) 1 no. Indicating voltmeter, flush mounted with scale 0 to 15 KV for connection to the potential

transformer.

c) 1 no. voltmeters selector switch with 6 (Six) positions flush mounted, rated voltage 500 Volts (50

Hz) rated current 15 Amps, front plate with inscription AB-BC-AC-AN-BN-CN.

d) 1 set, necessary supporting insulators and other accessories, wiring, fuses, heater etc.

e) The PT mounted on the 11KV TRANSFORMER INCOMING CUBICLES may also be offered.

274

7.1.5.6 FEATURES & ACCESSORIES

a) VCB should be restrike free. b) VCB should be trip free. c) Vacuum Interrupter shall be capable of short circuit current switching ≥ 100. d) Breaker trucks of different current ratings shall not be interchangeable. e) All current carrying parts shall be made of copper. f) Hand closing and tripping shall be done through manual levers. g) Manually operating devices for slow closing for inspection and maintenance. It shall not be

possible to slow close a breaker when in normal services. h) Each cubicle shall have ON-OFF indicator and provision for manual operation and necessary

interlocking. i) Protective relay shall be sufficient for over current and earth fault protection and shall be of

numerical programmable type. Accessories/Software required if any, Control & Protection Scheme drawings and Operation & Maintenance manual is within the scope of supply for each panel.

j) All indicating meters will be semi flush type with full view 240" scale range with intimate dial, black marketing and pointer with moving element with zero adjuster.

k) The painting shall be gray outside and glazed white inside (RAL 7032). l) All equipment and accessories shall be fully tropicalized. m) Necessary foundation bolts, spare heaters (installed and wire), manual handle for the breakers, test

jumpers, portable lamp, set of test plug for test terminals and draw-out type relay shall be supplied.

n) The complete panel and its accessories shall be made to the latest relevant IEC standards. o) VCB shall be removable, draw-out type floor mounted (Lower part of the Panel ) and all the

protective relays shall be mounted on the upper part of the panel. p) Rating plate and diagram plate having all information as per relevant IEC standard shall be made

of stainless steel and have engraved letters filled with black enamel paint. q) At least three sets relay & meter testing plug shall be supplied. r) Each VCB cubicles shall be complete according to the specification, features and bill of materials

but not limited to these items; the VCB cubicles should be complete in all respects, to make it fully operational. Electricaly & Mechanically interlocking shall be provided.

s) Tripping from protection to circuit breakers shall be through fast acting (<10 msec) Trip relays. Tripping from protection to circuit breakers shall be through Trip relays. Tripping from protection to circuit breakers shall be through Trip relays.

t) CT terminal block shall have isolation, shorting & jacking facility while PT terminal block shall have isolation & jacking facility.

u) Circuit Breaker control indicating switches and indicating lamps to indicate spring Charge/ Readiness for closing and healthy trip circuit indicating readiness for tripping.

v) Circuit Breaker shall have 2 trip coils, one used for control and the other for protection trip scheme. w) Indicating/Signaling Lamps shall be of LED type. x) Mimic diagram. The color and size of the mimic shall be as described below:

11 kV BLUE ½" X 1/8"

y) A copy of Control circuit scheme shall be laminated and fixed to the inner side of the door of the cubicle

z) Operation Counter for the circuit breaker. aa) Anti pumping feature shall be provided/ included. ab) Bidder shall supply related software (1 Original copy) and trouble shooting procedure manuals.

275

7.1.5.7. PROTECTIVE RELAYS

All Protective relays shall be numerical programmable type and shall comply relevant IEC or equivalent international standard.

All the protective relays shall be supplied from any of following manufacturers:-

a) ABB (Switzerland/Sweden/Finland). b) Siemens (Germany). c) ALSTOM (UK/France) d) Schneider (UK/ France) d) NR, China. Note: Related software & accessories is within the scope of supply. 7.1.5 .8. ENERGY METERS:

KWH meter shall 3-phase 4-wire, Numerical Programmable Multifunction KWH Meter of accuracy class 0.2 with the features for measuring the parameters viz. phase voltages, phase currents, system frequency, per phase & total KW with maximum demand, KVAR, Power factor etc.

All the energy meter shall be supplied from any of the following manufacturers:-

a) Siemens, Germany/Switzerland. b) AEG, Germany. c) ABB, Switzerland/Finland d) Itron, USA e) Elster, USA/ Romania f) Landis+ Gyr, Switzerland. g) Toshiba (Japan) h) Honeywell (USA)

Note: Manufacturer's authorization for Protective Relays & Energy Meters (KWh) shall furnish with the offer. Necessary software & accessories is within the scope of supply.

7.1.5 .9. CONSTRUCTION DETAILS

Each panel shall be fabricated from steel sheet (minimum 1.62 mm thick) with necessary steel member reinforcement to make the structure self supporting. All joints are to be welded and ground to be made smooth. Mounting brackets required shall be arranged inside the panel for mounting and fixing auxiliary devices and terminal blocks.

Instruments meters control switches and protective relays shall be mounted on the front panel only. Panel output mounting studs and support brackets shall be accurately located.

Finished panel surface shall be free of waves and other imperfections exterior panel surfaces shall be send blasted, ground smooth, filled, panel and finished with gray enamel. Interior surface shall be sand blasted, primed and finished with glass white enamel.

The LV panel shall be designed to facilitate entry of inter-panels control wires and cables. The LV & Breaker compartment doors shall be equipped with hinged formed door. The door shall be rigid and shall be equipped with three point latches. The breaker & busbar compartments shall be capable of withstanding internal faults.

276

The supplier shall furnish internal panel wiring and circuit protection. The supplier shall provide one 100W, 240, AC strip heater in the panel. The heater shall have a separate switch. Engraved name plate shall be provided at the top of the front enclosure.

7.1.5.10. PANEL WIRING:

The supplier shall provide internal wiring and connections, in accordance with the requirements of the following paragraph. All wiring used within the panel shall conform to the requirements of these specifications and shall be installed and tested at the factory. All wiring shall be neatly and carefully installed in wring gutters of raceway wiring raceway shall be plastic wiring duct with covers. Instrument wiring on the panel shall be numbered sequentially from the sources to the panel instrument and the number of the source equipment shall be used as a prefix for the individual wire numbers, wiring shall be terminated at terminal blocks plainly lettered or marked in accordance with the manufacturer’s connection diagrams.

Sufficient clearance shall be provided for all the leads. All the leads for external circuit wiring shall be connected to grounded terminal blocks located for convenient connection of external circuits.

Splices will not be permitted in panel wiring.

All the terminal block connections shall be made with ring type lugs. Pre-insulated ring type terminals with crimp guide or per-insulated slotted spring spade terminals shall be provided on devices equipped with individual fitted covers.

Arrangement of circuits on terminal block shall be such that all the connections for one circuit, plus any spare conductors, shall have terminal blocks adjacent to the split and shall be provided with wiring required to interconnect the split unit.

The size of the wiring used in the panel shall be conform to the following requirements:-

- Ampere meter and current transformer circuit : 4 Sq.mm. - All other wiring : 2.5 Sq.mm.

7.1.5.11. INDICATING LIGHTS

LED type indicating lights shall be of transparent glass lenses and appropriately sized resister. A lamp test push button shall be provided & fitted.

7.1.5.12. POWER SUPPLY DISCONNECT

Each panel mounted devices requiring AC or DC supply, shall have disconnecting devices (MCB). The MCBs used in DC control circuit shall have a rating of 10 A and 250 V. The fuses shall be modular type with Bakelite frame and reinforced retaining clips. 7.1.5.13. TERMINAL BLOCKS

Terminal blocks shall provided with white marking strips, circuit designation by the supplier shall be inscribed on the marking strip with black print, terminals in a quantity of not less than 25 percent of the interconnected

277

terminals in excess shall be provided on each terminal block for circuit modifications and for termination of all conductors in multi-conductor cable.

CT terminal blocks shall have isolation, shorting & jacking facility while PT terminal blocks shall have isolation & jacking facility. CT, PT, Control, Alarm, etc. wirings shall be separately grouped or segregated.

Terminal block shall be grouped in each panel for easy accessibility unrestricted by interference from structural members and instruments. Sufficient spaces shall be provided on each side of each terminal block to allow an orderly arrangement of all the lead to be terminated on the block.

7.1.5.14. INSTRUMENTS AND DEVICES

Indicating, analogue instruments shall be semi flush panel type with 1% percent accuracy class except for energy meters which shall be of 0.2. They shall be approximately 100 mm square with black 250 degree scales on a white back ground.

All AC instruments shall be designed for operation on 5A current transformers secondary and 110V (50 Hz) potential transformer secondary.

7.1.5.15. CONTROL AND DEVICES:

All switches shall be located at a convenient operating height and so constructed, mounted and wired to facilitate the maintenance of contracts without the need to disconnect wiring. handle type switches shall have locks incorporated in the design, control switches must be lockable in the inactive or neutral position and selector switches in all positions. Labels shall clearly indicate all positions and function of each switch.

7.1.5.16. Control Switches:

Control switches shall be of either the handle type and shall be arranged to operate clockwise when closing the circuit devices and anticlockwise when opening. Handle type switches shall be so designed that when released by the operator the handle and mechanism shall return automatically to the entered neutral position and interrupt the supply of current to the operating mechanism of the circuit device. All control switches shall have additional labeling giving the reference identification of the device.

7.1.5.17. Selector Switches:

Selector switches shall have spade type handles. Where key operated switches are specified these shall be operated by inserting and tuning the key to the required position. The key shall be removable in the 'OFF" position only.

7.1.5.18. ANNUNCIATOR RELAY

Each 11kV PCM Cubicle will be provided with 1 (one) set separate Annunciator (4x6 Window) and signaling relays and wiring with fuses. 2 nos. windows shall be kept spare.

7.1.5.19. INDICATING AMMETERS

Each 11kV PCM Cubicle will be provided with 3 Ammeters, analogue type (1 for each phase).

278

7.1.5.20. INDICATING VOLTMETERS

1 (one) voltmeter, analogue type with a multi-selector switch (phase to phase, phase to neutral, off) shall be installed on 11kV transformer panel.

7.1.5.21. Isolating Features:

The circuit breaker shall be connected to the busbars and feeder circuit through plug and soket type isolating devices. The devices shall be suitable for operation whilst the busbars or feeder circuits are live. The isolators shall comply with IEC 62271-102 standards. The following circuit breaker locations shall be provided and the description of each position shall be as per relavent IEC standards. The following position shall be provided as a minimum.:

ISOLATED (OR Maintanance)

Test Service: Mechanical and lamp indications shall be provided to show the location of the circuit breaker (ie. CB in test position, service position etc). Such indications shall be visible from the front of the equipments at all times.

7.1.5.22 EARTH SWITCH & EARTHING SYSTEM:

Earthing switches shall be arranged to permit safe maintanance of any section of the equipment when the remainder is live. Mechanical Interlock shall be provided such that when the cable is live the line earth switch shall not close. Local Electrical/ Mechanical position indicators shall be provided on all switches and shall be visible from the front side of the panel. The field contacts used for electrical indicators shall be contacts of limit switch which shall be actuated at the instant of earthing blades set at final position of operation.

7.1.5.23 EARTHING SYSTEM:

All metal parts other than those forming part of any electrical circuit shall be earthed to the earthing system. Any necessary terminals on any part of the equipment required for this purpose shall be provided by the Manufacturer. Earthing conductor cross shall be in accordance with the manufacturers standard which shall be proved with necessary type test reports. However, for 11 KV switchgear minimum 300mm2 cross section copper bar shall be employed for earthing. The copper earth bar shall run along the full length of the switch board and earthing studs shall be provided at not less than two points. The frame of the draw-out circuit breaker earthing truck shall be automatically connected to the switchgear bar through substantial plug type contact when the circuit breaker is in disconnection, service and test position.

7.1.5 .24 TRIP RELAY:

Following shall be the main features of a high speed tripping relays:

All tripping relays shall be of the heavy duty type suitable for panel mounting and shall have operating coils which are rated sufficiently to operate in conjunction with series flag relays. if necessary, normally closed contacts in series with the relay operating coil, shall be dealyed for a period which will allow series flag relays to operate satisfactorily. All other tripping contacts should be instantaneous i.e. no intentional time delay. The operating time shall not exceed 10microsecond at rated voltage, The operating range of the relay shall be from 70% to 120% of rated voltage. Electrical reset facilities shall be available for operation from remote and supervisory controls. High speed tripping relays shall prevent closing of the associated circuit breakers until reset. Wherever the tripping relay contacts need to break the d.c current, sufficiently rated magnetic blow out contacts or such approved means shall be used.

279

7.1.5 .25 SUPERVISION RELAYS:

7.1.5 .25.1 Trip Circuit and Protection Supply Supervision:

The trip circuit supervision function shall be part of control and protection unit provided in the switchgear. It shall be provided to monitor each of the trip circuits of all 11 KV breaker and each relays shall have sufficient contacts for visual/ audible alarm and indication purpose. The trip circuit supervision scheme shall provided continous supervision of the trip circuit on the circuit breaker in either the open or closed position and independent of local or remote selection at the local operating position. Relay elements shall be delayed on drop-off to prevents false alarms during faults on dc wiring on adjacent circuits, or due to operation of a trip relay contact . Series resistance shall be provided in trip supervision circuits to prevent mal tripping a circuit breaker if a relay element is short circuited. Relay alarm elemants shall be equipped with hand resetting flag indicators.

7.1.5 .25.2 D.C. SUPPLY RELAYS SUPERVISION:

Supervision relays are required for each protection supply, Main protection, Back-up and trip Relay Reset. Similarly for each trip circuit supply and for each alarm / indication supply. These supervision are to be independent of alarms from the trip circuit supervision scheme so that the operator can clearly didderentiate via the available alarms between loss of supply due to a blown fuse/ tripped MCB and failure of a trip. circuits supervision/ faulty supervision wiring.

7.1.5 .26 MIMIC BUS

Mimic bus material shall be brass, bronze or copper with enamel finished or anodized aluminum or plastic. The mimic bus and included symbols shall be shaped, colored and located as international standard. Light indicator showing position (opening/closing) of circuit breaker shall be installed.

The mimic bus shall be attached to the panel by mechanical devices, not with adhesive.

Attachment shall be closely spaced to hold all parts of the mimic bus firmly to the panel face.

Mimic bus shall be provided with the following dimensions and color code:-

Voltage Bus Color Thick Dimension (mm)

11 KV Black 3 12

7.1.5 .27 TESTS AT MANUFACTURERS WORKS: 7.1.5 .27.1 GENERAL Functional electrical, material and mechanical tests shall be carried out at manufacturers’ premises. The extent and method of recording the results shall be agreed by the Purchaser in ample time to enable the tests to be satisfactorily witnessed or to make any changes to the proposed program of tests.

7.1.5 .27.2. MATERIAL TESTS:

The supplier shall provide test pieces free of charge as required to enable the quality of the material to be determined at the supplier’s expense. Purchaser may at its own discretion and by specific arrangement accept certified particulars of tests carried out in the absence of his authorized representative. 7.1.5 .27.3. TYPE TEST:

Type tests are required on all items to prove the general design of the goods offered. The Bidders shall submit the type test report of offered item from internationally reputed independent testing laboratory.

280

7.1.5 .27.4. ROUTINE TESTS:

All items shall be subjected to routine tests in accordance with the relevant latest version of IEC-62271-200, IEC-60298 IEC-60255 standards at the manufacturers works and shall include, but not be limited to, an operational test.

7.1.5 .28 TECHNICAL ORIENTATION AND QUALITY TEST WITNESS:

The Purchaser shall have the right to inspect/ Test the goods/materials to confirm their conformity to the Technical specification. The purchaser shall be entitled at all reasonable time during manufacture to inspect, examine and test of goods/ materials at the manufacturers’ premises, workmanship and performance.

The following test (not limited to) shall be carried out as per latest version of IEC-62271-200, IEC-60298 IEC-60255 and other relevant IEC standard. Among others, the following test shall be included but not limited to:-

a) Di-electric test on the main circuit. b) Test on Auxilary and control circuits. c) Measurement of the resistance of the main circuit d) Tightness test. e) Design and visual (Physical) checks f) Electrical and Mechinical operation test. g) Relay, control and protection scheme functional check.

Test shall be performed in accordance with the relevant IEC/BS Standards and shall be complied with offered Guaranteed Technical Particulars. All expenses for such tests shall be borne by the supplier, which shall deemed to be included in the offered price.

The Supplier shall, after consulting the purchaser, give the Purchaser reasonable notice in writing of the date on and the place at which any material or equipment will be ready for testing as provided in the contract and unless the purchaser shall attend at the place so named on date, which the supplier has stated in his notice, the supplier may proceed with the tests, which shall be deemed to have been made in the purchaser’s presence, and shall forth with forward to the purchaser duly certified copies of test readings.

When the purchaser intends to attend the test he shall promptly inform the supplier accordingly in writing, so that he can take action. The purchaser shall give the supplier timely notice in writing of his intention to attend the test.

Where the supplier provides for tests on the premises of the supplier or of any manufacturer of the supplier, except where otherwise specified, shall provide free of charge such assistance, labor, materials, electricity, fuel, stores, apparatus and instruments as may be requisite and as may be reasonably demanded to carry out such test efficiently. These test shall be performed as per relevant IEC/BS Standard or equivalent and only routine tests as agreed upon, will be performed.

As and when the purchaser is satisfied that any materials/equipment shall have passes the tests referred to in this clause, purchaser shall notify the contractor in writing to that effect.

Should any inspected/tested goods fail to conform to the specification, the Purchaser shall have the right to reject any of the item or complete batch if necessary. In that case Supplier have to replace the Equipment and to make good of them without any financial involvement to the Purchaser. In case any of the Equipment found not conforming with the specification at the time of post landing Inspection, the supplier will in no way be relieved

281

from the responsibility of replacing them on making them good at their own cost, despite the Equipment were found good at the time of Factory Acceptance Test. Nothing in this clause shall in any way release the supplier from any warranty or other obligations under the contract.

No goods shall be packed, prepared for shipment/delivery unless it has been approved and written instruction have been received by the Purchaser.

7.1.5 .29 POST LANDING INSPECTION : Post landing inspection shall be done immediately after arrival of the goods/materials at the designated store of

BPDB; the Engineer & representative from consignee shall conduct Post Landing Inspection in presence of the

representative of Supplier. The program of such inspection shall be intimated to the representative of Supplier by

BPDB upon arrival of the materials at BPDB store of the Inspector(s) to be selected for test witnessing. The

inspection team shall conduct the following test:

(i) Design and visual (Physical) Inspection and quantity checks.

Any defect or damage have been found at post-delivery inspection, the defective or damaged panels/ materials/

goods to be repaired/ replaced by the Bidder/ supplier at his own cost.

282

7.1.6 Technical Specification of 33KV Isolator (1250A) with Earth blade

7.1.6.1 General Specification:

1. Installation Outdoor

2. Type Air

3. Construction Open

4. Operation Gang

5. Operating Mechanism Manual

6. Mounting Position Vertical on supporting structure.

7. Number of Pole 3 (Three)

8. Frequency 50 Hz

9. System Nominal Voltage 33 KV

10. System Maximum Voltage 36 KV

11. Basic Insulation Level 170 KV

12. Rated continuous Current

a) for 16/20MVA 1250 A

13. Rated Short Time Withstand Current 25 KA (3 Sec.)

14. Rated 1 minute power frequency

withstand voltage, kV (rms)

70KV

15. Standard Design, Manufacture, Testing, Installation and

Performance shall be in accordance to the latest

editions of the relevant IEC standards.

A. FEATURES

- Single-Break Pattern [Vertical break or Horizontal break (centre break)], OFF load type.

- Channel type mounting base insulator, blast.

- Coupling tubes for gang operation and adjustable operating rod with insulating link and

intermediate guide for operating rod.

- Auxiliary switch, operated by the phase coupling tube, to control circuits for operating

indicators, alarms, electrical inter-locking with the respective breaker to ensure that the

isolator can only be operated when the breaker is in “OFF’ position etc. with at least

10% spare contacts.

- Terminal connectors shall be suitable for ACSR Merlin/ Gross Beak/ HAWK conductor as

required.

- Earthing steel pads with provision for earth lead.

- Glands for multi-core control cables.

- Provision for pad locking in “ON” & “OFF” position.

- Provision of key interlocking.

- Galvanized Nuts, bolts & all accessories for mounting on structures.

- Interlocking magnet for electrical interlocking.

- All ferrous parts shall be hot dipped galvanized after completion of machining.

Galvanizing shall be in accordance with BS-729.

- All control devices shall be suitable for operation on 110 V DC supplies from Sub-station.

- Operating mechanism shall be fully tropicalized and housed in waterproof housing.

- Complete supporting steel structure.

283

- Isolating devices shall be accordance with IEC-60129. They shall be complete with

supporting steel work and installed to maintenance of any section of the sub-station

plant when the remainder is alive and shall be so located that the minimum safety

clearances are always maintained.

- The air gap between terminals of the same pole with the isolator open shall be of a

length to withstand a minimum impulse voltage wave of 115. Percent of the specified

impulse insulation rating to earth

- Isolating switches shall be designed for life operation and isolators shall be hands

operated. Where used for feeders they shall be capable of switching transformer-

magnetizing currents. Main contacts shall be of the high-pressure line type and acing

contacts.

- All feeder isolators shall be fitted with approved three phase link earthing devices,

mechanically, coupled or interlocked with the main isolator so that the earthing device

and main isolator con not be closed at the same time.

- Isolator operating mechanism shall be of robust construction, carefully fitted to ensure

free action and shall be un-effected by the climatic conditions at site. Mechanism shall be

as simple as possible and comprise a minimum of bearing and wearing parts. Approved

grease lubricating devices shall be fitted to all principal bearings. The mechanism shall

be housed in weatherproof enclosure complete with auxiliary switches, terminal blocks

and cable gland plates. All steel and malleable iron parts including the support

steelwork shall be galvanized as per BS-729.

B. Blades:

All metal parts shall be of non rusting and non corroding material. All current carrying

parts shall be made from high conductivity electrolytic copper/aluminium. Bolts, screws

and pins shall be provided with lock washers. Keys or equivalent locking facilities if

provided on current carrying parts, shall be made of copper silicon alloy or stainless

steel or equivalent. The bolts or pins used in current carrying parts shall be made of non

corroding material. All ferrous castings except current carrying parts shall be made of

malleable cast iron or cast steel. No grey iron shall be used in the manufacture of any

part of the isolator. The live parts shall be designed to eliminate sharp joints, edges and

other corona producing surfaces, where this is impracticable adequate corona shield

shall be provided. Isolators and earthing switches including their operating parts shall

be such that they cannot be dislodged from their open or closed positions by short

circuit forces, gravity, wind pressure, vibrations, shocks, or accidental touching of the

connecting rods of the operating mechanism. The switch shall be designed such that no

lubrication of any part is required except at very infrequent intervals i.e. after every

1000 operations or after 5 years whichever is earlier.

C. Base :

Each isolator shall be provided with a complete galvanised steel base provided with

holes and designed for mounting on a supporting structure.

D. Supporting Structure

All isolators and earthing switches shall be rigidly mounted in an upright position on

their own supporting structures. Details of the supporting structures shall be furnished

284

by the successful tenderer. The isolators should have requisite fixing details ready for

mounting them on switch structures.

7.1.7 Technical Specification of 33KV Isolator (1250A) without Earth blade

7.1.7.1 General Specification:

1. Installation Outdoor

2. Type Air

3. Construction Open

4. Operation Gang

5. Operating Mechanism Manual

6. Mounting Position Vertical on supporting structure.

7. Number of Pole 3 (Three)

8. Frequency 50 Hz

9. System Nominal Voltage 33 KV

10. System Maximum Voltage 36 KV

11. Basic Insulation Level 170 KV

12. Rated continuous Current

a) for 16/20MVA S/S 1250 A

13. Rated Short Time Withstand Current 25 KA (3 Sec.)

14. Rated 1 minute power frequency

withstand voltage, kV (rms)

70KV

15. Standard Design, Manufacture, Testing, Installation and

Performance shall be in accordance to the latest

editions of the relevant IEC standards.

A. FEATURES

- Single-Break Pattern [Vertical break or Horizontal break (centre break)], OFF load type.

- Channel type mounting base insulator, blast.

- Coupling tubes for gang operation and adjustable operating rod with insulating link and

intermediate guide for operating rod.

- Auxiliary switch, operated by the phase coupling tube, to control circuits for operating

indicators, alarms, electrical inter-locking with the respective breaker to ensure that the

isolator can only be operated when the breaker is in “OFF’ position etc. with at least 10%

spare contacts.

- Terminal connectors shall be suitable for ACSR Martin/ Gross Beak/ HAWK conductor

as required.

- Earthing steel pads with provision for earth lead.

- Glands for multi-core control cables.

- Provision for pad locking in “ON” & “OFF” position.

- Provision of key interlocking.

- Galvanized Nuts, bolts & all accessories for mounting on structures.

- Interlocking magnet for electrical interlocking.

- All ferrous parts shall be hot dipped galvanized after completion of machining.

Galvanizing shall be in accordance with BS-729.

- All control devices shall be suitable for operation on 110 V DC supplies from Sub-station.

285

- Operating mechanism shall be fully tropicalized and housed in waterproof housing.

- Complete supporting steel structure.

- Isolating devices shall be accordance with IEC-60129. They shall be complete with

supporting steel work and installed to maintenance of any section of the sub-station

plant when the remainder is alive and shall be so located that the minimum safety

clearances are always maintained.

- The air gap between terminals of the same pole with the isolator open shall be of a

length to withstand a minimum impulse voltage wave of 115. Percent of the specified

impulse insulation rating to earth.

- Isolating switches shall be designed for life operation and isolators shall be hands

operated. Where used for feeders they shall be capable of switching transformer-

magnetizing currents. Main contacts shall be of the high-pressure line type and acing

contacts.

- All feeder isolators shall be fitted with approved three phase link earthing devices,

mechanically, coupled or interlocked with the main isolator so that the earthing device

and main isolator con not be closed at the same time.

- Isolator operating mechanism shall be of robust construction, carefully fitted to ensure

free action and shall be un-effected by the climatic conditions at site. Mechanism shall be

as simple as possible and comprise a minimum of bearing and wearing parts. Approved

grease lubricating devices shall be fitted to all principal bearings. The mechanism shall

be housed in weatherproof enclosure complete with auxiliary switches, terminal blocks

and cable gland plates. All steel and malleable iron parts including the support

steelwork shall be galvanized as per BS-729.

B. Base :

Each isolator shall be provided with a complete galvanised steel base provided with

holes and designed for mounting on a supporting structure.

C. Supporting Structure

All isolators and earthing switches shall be rigidly mounted in an upright position on

their own supporting structures. Details of the supporting structures shall be furnished

by the successful tenderer. The isolators should have requisite fixing details ready for

mounting them on switch structures.

286

7.1.8 Technical Specification of 33 kV Off-Load Fused Isolator for auxiliary transformer .

A. General :

Installation Outdoor Type Air Construction Open Operation Gang Purpose For auxiliary 200/ 50 KVA Transformer Operating Mechanism Manual Base Mounting Position Vertical Number of Pole 3 (Three) Frequency 50Hz System Nominal Voltage 33KV System Maximum Voltage 36KV Continuous Current 200 A/ 50 A Fuse Rating 5A/ 2 A Fuse Type HRC Cartridge Rated Short Time Withstand Current 25KA 3 Sec.

Standard

Design, Manufacture, Testing, Installation and Performance shall be in accordance to the latest editions of the relevant IEC standards.

Features - Single Break Pattern [Vertical break). - Channel type mounting base, insulator & phase coupling tube for gang

operation and adjustable operating rod with insulating link and intermediate guide for operating rod.

- Terminal connectors shall be suitable for ACSR Merlin/ Gross Beak/ HAWK conductor as required.

- Glands for multi-core control cables. - Provision for pad locking in “ON” & “OFF” position. - Galvanized Nuts, bolts & all accessories shall be required for mounting the

isolator on structure. - All ferrous parts shall be hot dipped galvanized after completion of machining.

Galvanizing shall be in accordance with BS-729. - 2 sets of spare fuse links (6 Nos.) shall be supplied with each set of isolator. - All steel supporting structures for mounting on the structures. - For enclosed fuses a positive mechanical indication shall be provided to

indicate a blown fuse. - The design shall provide reasonable protection against accidental earthing by

animals or birds. - All the movable current carrying contacts shall be silver plated. - Arcing horn if the unit is combined. - Disconnecting blade has continuous current rating as specified. - Isolating devices shall be accordance with IEC-129. They shall be complete

with supporting steel work and installed to maintenance of any section of the

287

sub-station plant when the remainder is alive and shall be so located that the minimum safety clearances are always maintained.

- The air gap between terminals of the same pole with the isolator open shall be of a length to withstand a minimum impulse voltage wave of 115 percent of the specified impulse insulation rating to earth.

- Isolating switches shall be designed for live operation and isolators shall be hands operated. Where used for feeders they shall be capable of switching transformer-magnetizing currents. Main contacts shall be of the high-pressure line type and arcing contacts, if provided, shall be to the Engineer’s approval.

- Service conditions require that isolating switches shall remain alive and in continuous service for periods of up to 2 years in the climatic conditions specified without operation or maintenance. These contacts shall carry their rated load and short circuit currents without over heating or welding and at the end of the two years period the maximum torque required at the operating handle to open 3-phase isolator shall not exceed 350 NM.

- All feeder isolators shall be fitted with approved three phase link earthing devices, mechanically, coupled or interlocked with the main isolator so that the earthing device and main isolator con not be closed at the same time.

- Isolator operating mechanism shall be of robust construction, carefully fitted to ensure free action and shall be un-effected by the climatic conditions at site. Mechanism shall be as simple as possible and comprise a minimum of bearing and wearing parts. Approved grease lubricating

- devices shall be fitted to all principal bearings. The mechanism shall be housed in weatherproof enclosure complete with auxiliary switches, terminal blocks and cable gland plates. All steel and malleable iron parts including the support steelwork shall be galvanized as per BS-729.

- At least two pairs of auxiliary contacts for each isolator shall be provided.

7.1.9 Technical Specification Of 33 kV Off-Load Isolator Without Earth Blade

for Bus Section.

7.1.9.1 General

1. Installation Outdoor

2. Type Air

3. Construction Open

4. Operation Gang

5. Operating Mechanism Manual

6. Mounting Position Vertical for Bus Isolator & Horizontal for Bus Coupler on

supporting structure

7. Number of Pole 3 (Three)

8. Frequency 50 Hz

9. System Nominal Voltage 33 KV

10. System Maximum Voltage 36 KV

11. Basic Insulation Level 170 KV

12. Rated Normal Current 800A for Bus Isolator & 1250 A for Bus Coupler

288

13. Rated Short Time Withstand Current 25 KA (3 Sec.)

14. Standard Design, Manufacture, Testing, Installation and

Performance shall be in accordance to the latest editions

of the relevant IEC standards.

15.FEATURES

i) Single-Break Pattern [Vertical break or Horizontal break (Centre break)], OFF load type.

ii) Channel type mounting base insulator, blast.

iii) Coupling tubes for gang operation and adjustable operating rod with insulating link and

intermediate guide for operating rod.

iv) Auxiliary switch, operated by the phase coupling tube, to control circuits for operating

indicators, alarms, electrical inter-locking with the respective breaker to ensure that

the isolator can only be operated when the breaker is in “OFF’ position etc. with at

least 10% spare contacts.

v) Terminal connectors shall be suitable for ACSR Merlin/ Gross Beak/ HAWK conductor

as required.

vi) Earthing steel pads with provision for earth lead.

vii) Glands for multi-core control cables.

viii) Provision for pad locking in “ON” & “OFF” position.

ix) Provision of key interlocking.

x) Galvanized Nuts, bolts & all accessories for mounting on structures.

xi) Interlocking magnet for electrical interlocking.

xii) All ferrous parts shall be hot dipped galvanized after completion of machining.

xiii) Galvanizing shall be in accordance with BS-729.

xiv) All control devices shall be suitable for operation on 110 V DC supplies from Sub-

station.

xv) Operating mechanism shall be fully tropicalized and housed in waterproof housing.

xvi) Complete supporting steel structure.

xvii) Isolating devices shall be accordance with IEC-129. They shall be complete with supporting

steel work and installed to maintenance of any section of the sub-station plant when the

remainder is alive and shall be so located that the minimum safety clearances are always

maintained.

xviii)The air gap between terminals of the same pole with the isolator open shall be of a length to

withstand a minimum impulse voltage wave of 115. Percent of the specified impulse insulation

rating to earth.

xix) Isolating switches shall be designed for life operation and isolators shall be hands operated.

Where used for feeders they shall be capable of switching transformer-magnetizing currents.

Main contacts shall be of the high-pressure line type and acing contacts. xx) Isolator operating

mechanism shall be of robust construction, carefully fitted to ensure free action and shall be un-

effected by the climatic conditions at site. Mechanism shall be as simple as possible and

comprise a minimum of bearing and wearing parts. Approved grease lubricating devices shall be

fitted to all principal bearings. The mechanism shall be housed in weatherproof enclosure

complete with auxiliary switches, terminal blocks and cable gland plates. All steel and malleable

iron parts including the support steelwork shall be galvanized as per BS-729.

\

289

7.1.10 Technical Specification of 33 kV Off-Load Isolator (800A) With Earth Blade.

7.1.10.01 General

1. Installation Outdoor Sub-station

2. Type Air

3. Construction Open

4. Operation Gang

5. Operating Mechanism Manual

6. Mounting Position Vertical

7. Number of Pole 3 (Three)

8. Frequency 50 Hz

9. System Nominal Voltage 33 KV

10. System Maximum Voltage 36 KV

11. Basic Insulation Level 170 KV

12. Rated Normal Current 800 A

13. Rated Short Time Withstand Current 25 KA (3 Sec.)

14. Standard Design, Manufacture, Testing, Installation and Performance

shall be in accordance to the latest editions of the relevant IEC

standards.

15. Features

The line isolators shall be single break Pattern [Vertical break or Horizontal break (centre break)]

pattern off-load type with manual operating mechanism for the earth blade. There shall be

interlocking arrangement with the breaker to ensure that the Isolator can only be operated with

breaker in “OFF” position. Necessary controls, accessories and auxiliary operating mechanism for

manual operation shall be provided in water proof outdoor boxes.

- The earthing device shall be gang operated & integral with the switch. The unit shall be complete

with channel type mounting base, insulators, and phases coupling tube for gang operation and

adjustable operating rod with insulating link and intermediate guide for operating rod.

- Auxiliary switch operated by the phase coupling tube shall be provided to control circuits for

operating devices like indicators/alarms & interlocking with 100% spare contacts.

- Terminal connectors shall be suitable for ACSR Merlin/ Gross Beak/ HAWK conductor as required.

- Earthing steel pads shall be provided with provision of earth leads.

- Cable glands for multi-core control/ power cables as required.

- There shall be provisions for pad locking in “ON” & “OFF” position.

- Provision of key interlocking.

- Mechanical interlocking between earthing device & the switch shall be provided.

- All accessories, nuts, bolts etc. required for mounting the isolator on structure as required.

- All ferrous parts shall be hot dip galvanized after completion of machining. Galvanizing shall be in

accordance with BS-729.

290

- All control devices shall be suitable for operation from 110 Volts DC available in the control room.

- Isolator and earthing devices shall be accordance with IEC-129. They shall be complete with

supporting steelwork and installed to permit maintenance of any section of the sub-station plat when

the remainder is alive and shall be so located that the minimum safety clearances are always

maintained.

- The air gap between terminals of the same pole with the isolator open shall be of a length to

withstand a minimum impulse voltage wave of 115 percent of the specified impulse insulation rating

to earth.

- Isolating switches shall be designed for live operation and isolators shall be hands operated. Where

used for feeders they shall be capable of switching transformer magnetizing currents main contacts

shall be of the high-pressure line type and acing contacts.

7.1.12 11KV DROP OUT OPEN TYPE FUSED COMBINATION DISCONNECT

AND BY-PASS SWITCH : 7.1.12.01 GENERAL Application : 11KV Auto recloser

Installation : Outdoor structure mounted

Type

: Drop out open type fused combination disconnect and by-pass SWITCH

Operating mechanism : Manual

Number of poles : 3 (three)

System frequency : 50 Hz

Rated voltage : 11 KV

Max system voltage : 12 KV

Rated isolator current (continuous) : 630 amperes

Rated short time current : 25 KA, 3 seconds

Maximum ambient temperature : 450C.

Basic insulation level (Min) : 75 KV Standards

:

Performance design & testing shall be in accordance to latest revision of BS- 5253 or IEC-129 or equivalent International standards unless otherwise specified herein.

291

FEATURES & ACCESSORIES : a) Isolating switch shall be provided with three bladed by-pass switch & fused disconnect

switch. b) The design shall provide reasonable protection against accidental earthling by animals or

birds. c) Terminal shall be tin plated to accommodate AAC/ACSR/Copper conductor of diameter

from 9.3 mm to 14.5mm. d) All movable current carrying contacts shall be silver-plated. e) Channel for structure mounting with nuts, bolts, washers etc. f) Nuts, bolts and all accessories required for mounting the insulator on structure. g) All ferrous parts shall be hot dip galvanized as per BS : 729. h) Hot stick is to be provided with each set for disconnecting hot line clamps. 7.1.13 11KV OFF LOAD ISOLATOR (630A) WITHOUT EARTHING BLADE

7.1.13.01. GENERAL :

1.1 Installation : Outdoor substation

1.2 Type : Air

1.3 Construction : Open

1.4 Operating mechanism : Manual

1.5 Operation : Gang

1.6 Base mounting position : Vertical on supporting structure.

1.7 Number of poles : 3 (Three), gang operated

1.8 System frequency : 50 Hz

1.9 Rated voltage : 11 KV

1.10 Rated normal current : 630 amperes

1.11 Rated short time current : 25 KA, 3 second

1.12 Rated making current : 50 KA (peak)

1.13 Basic insulation level (Min) : 75 KV

1.14 Standards

:

Performance design & testing shall be in

accordance to latest revision of BS-5253

or IEC-129 or equivalent international

standards unless otherwise specified

herein

292

7.1.13.2. FEATURES & ACCESSORIES:

a) The line isolators shall be single break Pattern Vertical break (centre break) pattern

off-load type with manual operating mechanism for the earth blade.

b) The earthing device shall be gang operated & integral with the switch. The unit shall

be complete with channel type mounting base, insulators, and phases coupling tube

for gang operation and adjustable operating rod with insulating link and intermediate

guide for operating rod.

c) Terminal connectors shall be suitable for ACSR Merlin/ Grosbeak/ Hawk conductor

as required.

d) There shall be provisions for pad locking in “ON” & “OFF” position.

e) Operating mechanism shall be fully tropicalized and housed in waterproof housing

with provision of key interlocking. Isolator operating mechanism shall be of robust

construction, carefully fitted to ensure free action and shall be un-effected by the

climatic conditions at site. Mechanism shall be as simple as possible and comprise a

minimum of bearing and wearing parts. Approved grease lubricating devices shall be

fitted to all principal bearings. The mechanism shall be housed in weatherproof

enclosure. All steel and malleable iron parts including the support steelwork shall be

galvanized as per BS-729.

f) Mechanical interlocking between earthing device & the isolator (with earthswitch)

shall be provided.

g) All accessories, nuts, bolts etc. required for mounting the isolator on structure as

required shall be provided.

h) Isolator and earthing devices shall be accordance with IEC-129. They shall be

complete with supporting steelwork and installed to permit maintenance of any

section of the sub-station plat when the remainder is alive and shall be so located

that the minimum safety clearances are always maintained.

i) The air gap between terminals of the same pole with the isolator open shall be of a

length to withstand a minimum impulse voltage wave of 115 percent of the specified

impulse insulation rating to earth.

j) Isolators shall be designed for live operation and shall be hands operated. Where

used for feeders they shall be capable of switching transformer magnetizing currents

main contacts shall be of the high Pressure line type and acing contacts.

k) Diagram plate and rating nameplate shall be provided. Rating plate and diagram

plate shall be made of stainless steel and have engraved letters filled with blank

enamel paint mentioning manufacturer’s name, client name, year of manufacturing,

contract no & model no, rating, etc.

7.1.14 11KV Off-load Isolator with Earth-blade:

11KV Off-load Isolator with Earth-blade as specified shall be conforming to the latest edition of the following standards for operation under local ambient conditions. Design, Manufacture, Testing and Performance of the cable shall be in accordance with the IEC-60129 or equivalent International standards.

293

7.1.14.1 Technical Specification of 11 kV Off-Load Isolator With Earth

Blade:

A General

1. Installation Outdoor Sub-station

2. Type Air

3. Construction Open

4. Operation Gang

5. Operating Mechanism Manual

6. Mounting Position Vertical/Horizontal

7. Number of Pole 3 (Three)

8. Frequency 50 Hz

9. System Nominal Voltage 11 KV

10. System Maximum Voltage 12 KV

11. Basic Insulation Level 75 KV

12. a) Rated Normal Current 800 A

13. Rated Short Time Withstand Current 25 KA (3 Sec.)

14. Standard Design, Manufacture, Testing,

Installation and Performance shall be in

accordance to the latest editions of the

relevant IEC-60129 standards.

B FEATURES & ACCESSORIES:

(a)The line isolators shall be single break Pattern [Vertical break or Horizontal break

(centre break)] pattern off-load type with manual operating mechanism for the earth

blade. There shall be interlocking arrangement with the breaker to ensure that the

Isolator can only be operated with breaker in “OFF” position. Necessary controls,

accessories and auxiliary operating mechanism for manual operation shall be provided

in water proof outdoor boxes.

(b)The earthing device shall be gang operated & integral with the switch. The unit shall

be complete with channel type mounting base, insulators, and phases coupling tube for

gang operation and adjustable operating rod with insulating link and intermediate guide

for operating rod.

(c) Auxiliary switch operated by the phase coupling tube shall be provided to control

circuits for operating devices like indicators/alarms & interlocking with 100% spare

contacts.

(d) Terminal connectors shall be suitable for ACSR Merlin/ Gross Beak/ HAWK

conductor as required.

(e) Earthing steel pads shall be provided with provision of earth leads.

(f) Cable glands for multi-core control/ power cables as required.

294

(g) There shall be provisions for pad locking in “ON” & “OFF” position.

(h) Operating Mechanism Shall be fully Tropicallized and housed in waterproof housing with

Provision of key interlocking.

(i) Mechanical interlocking between earthing device & the Isolator (With Earth switch)

shall be provided.

(j) All accessories, nuts, bolts etc. required for mounting the isolator on structure as

required shall be provided.

(k) All ferrous parts shall be hot dip galvanized after completion of machining. Galvanizing

shall be in accordance with BS-729.

(l) All control devices shall be suitable for operation from 110 Volts DC available in the

control room.

(m) Isolator and earthing devices shall be accordance with IEC-60129. They shall be

complete with supporting steelwork and installed to permit maintenance of any section of

the sub-station plat when the remainder is alive and shall be so located that the minimum

safety clearances are always maintained.

(n) The air gap between terminals of the same pole with the isolator open shall be of a

length to withstand a minimum impulse voltage wave of 115 percent of the specified impulse

insulation rating to earth.

(o) Isolator shall be designed for live operation and isolators shall be hands operated. Where

used for feeders they shall be capable of switching transformer magnetizing currents main

contacts shall be of the high-pressure line type and acing contacts.

(p) Isolator shall be designed for live operation and isolators shall be hands operated. Where

used for feeders they shall be capable of switching transformer magnetizing currents main

contacts shall be of the high-pressure line type and acing contacts.

(q) Isolator Operating Mechanism shall be Robust Construction, Carefully Fitted to ensure

free action and shall be un-effected by the climatic condition at site Mechanism Shall be as

simple as possible and comprise a minimum of bearing and wearing Parts. Approved

grease lubricating device shall be fitted to all principal bearings. The Mechanism shall be

housed in weather proof enclosure with Auxiliary Switches, Terminal blocks and cable

gland plates. All steel and malleable iron parts including the supports steel work shall be

Galvanized as per BS-729.

(r) Diagram Plate and rating nameplate shall provide. Rating Plate and diagram plate shall

be made of Stainless Steel and have engraved letters filled with blank enamel paint

mentioning Manufacturers name, Client Name with bold, Years of Manufacturing, and

Contract No. Model No & Rating etc.

295

7.1.15 33KV Current Transformer

GENERAL TECHNICAL PARTICULARS:

1. Application Metering and Protection

2. Installation Outdoor.

3. Construction Sealed Tank

4. Insulation Oil

5. Number of Phase Single

6. Rated Frequency 50 Hz

7. Mounting On Supporting Structure

8. System Primary Rated Voltage 33 kV Phase to Phase

9. Maximum System Voltage 36kV Phase to Phase

10. System Earthing Effectively earthed

11. Basic Insulation Level (1.2/50 sec.) 170 kV

12. Power Frequency Withstand Voltage (1 min. 50 Hz).

70 kV

13. 33 kV Feeder Ratio:

for 2x 10/13MVA S/S 400-800/5-5A

transformer Feeder Ratio:

for 10/13MVA S/S 300-600/5-5-5A

14. Primary Single Winding

15. Secondary Double Winding

16. Accuracy Class 0.2 for Measurement, 5P20 for Protection.

17. Burden 30VA

18. Short Time Current Rating 25 kA for 3 Sec.

19. Extended Current Rating 120% of Rated Current

20. Over Current Rating < 10 A

21. Creepage Distance 25 mm/ KV (minimum)

22. Standard

Design, Manufacture, Testing, Installation and Performance shall be in accordance to the latest editions of the relevant IEC 60044-1 standards.

B FEATURES & ACCESSORIES:

a) Current transformer shall have porcelain outdoor type bushing.

b) Terminal connectors provided, shall be suitable for ACSR Merlin/ Grosbeak/ Hawk

conductor as required.

c) The equipment must be tropicalized and suitable for the outdoor location.

d) Galvanized nuts, bolts and all accessories required for mounting on structure.

e) All ferrous parts shall be hot-dip galvanized after completion of machining.

Galvanizing shall be in accordance with BS-729.

f) Each terminal shall have cadmium-plated nuts and bolts.

g) Sealing/locking arrangement for the secondary terminal box shall be provided.

296

h) Diagram plate and rating nameplate shall be provided. Rating plate and diagram

plate shall be made of stainless steel and have engraved letters filled with blank

enamel paint mentioning manufacturer’s name, client name, year of manufacturing,

contract no & model no, rating, etc..

i) Supporting clamps, all accessories shall be provided with the CT's for installation

on supporting gantry structure for line feeders CT's.

7.1.16 11 KV Current Transformer .

A GENERAL TECHNICAL PARTICULARS:

1. Application Metering and Protection

2. Installation Outdoor.

3. Construction Sealed Tank

4. Insulation Oil

5. Number of Phase Single

6. Rated Frequency 50 Hz

7. Mounting On Supporting Structure

8. System Primary Rated Voltage 11 kV Phase to Phase

9. Maximum System Voltage 12 kV Phase to Phase

10. System Earthing Effectively earthed

11. Basic Insulation Level (1.2/50 sec.) 75 KV

12. Power Frequency Withstand Voltage (1 min.

50 Hz).

28 KV

13. 11 kV transformer Feeder CT Ratio:

for 16/20MVA S/S 1600-800/5-5-5A

11 kV BUS CT Ratio:

for 16/20MVA S/S 1800-900/5-5A

11 kV outgoing Feeder CT Ratio:

for 630A 400-200/5-5A

for 1250A 800-400/5-5A

14. Primary Single Winding

15. Secondary Double Winding

16. Accuracy Class 0.2 for Measurement, 5P20 for

Protection.

17. Burden: 30VA

18. Short Time Current Rating 25 kA for 3 Sec.

19. Extended Current Rating 120% of Rated Current

20. Over Current Rating < 10 A

21. Creepage Distance 25 mm/ KV (minimum)

22. Standard Design, Manufacture, Testing,

297

Installation and Performance shall be in

accordance to the latest editions of the

relevant IEC 60044-1 standards.

B FEATURES & ACCESSORIES:

a) Current transformer shall have porcelain outdoor type bushing.

b) Terminal connectors provided, shall be suitable for ACSR Merlin/ Grosbeak/ Hawk

conductor as required.

c) The equipment must be tropicalized and suitable for the outdoor location.

d) Galvanized nuts, bolts and all accessories required for mounting on structure shall be

provided.

e) All ferrous parts shall be hot-dip galvanized after completion of machining.

Galvanizing shall be in accordance with BS-729.

f) Each terminal shall have cadmium-plated nuts and bolts.

g) Sealing/locking arrangement for the secondary terminal box shall be provided.

h) Diagram plate and rating nameplate shall be provided. Rating plate and diagram plate

shall be made of stainless steel and have engraved letters filled with blank enamel paint

mentioning manufacturer’s name, client name, year of manufacturing, contract no &

model no, rating, etc..

i) Supporting clamps, all accessories shall be provided with the CT's for installation on

supporting gantry structure for line feeders CT's.

298

7.1.17 Technical Specification of single phase 33KV Potential Transformer 7.1. 33.1 GENERAL TECHNICAL PARTICULARS:

1. Application Metering and Protection

2. Installation Outdoor 3. Insulation Oil 4. Type Voltage Induction 5. Construction Oil Tank 6. Number of Phase Singe Phase (1Set=3Nos) 7. Frequency 50 Hz

8. Mounting Mounted Supporting on Gantry Structure Mounted 9. System Primary Rated Voltage 33 kV (Phase to Phase)

10. System Primary Maximum Voltage 36 kV (Phase to Phase) 11. System Earthlings Effectively earthed 12. Basic Insulation (Impulse withstand

Voltage) 170 kV

13. Power Frequency Withstand Voltage 70 kV

14. The neutral end of primary winding, for direct connection to ground

Insulated to withstand the 10 kV low frequency test.

15. Type of Secondary Winding Double Winding 16. Transformation Ratio (33/√3)/ (0.11/√3)/ (0.11/√3) kV

17. Creepage Distance 25 mm/ kV (minimum)

18. Rated Secondary Burden 30 VA 19. Voltage limit factor 1.2 continuous 20. Class of Accuracy 0.2 for metering and 3P for protection.

21. Standard Design, Manufacture, Testing, Installation and Performance shall be in accordance to the latest editions of the relevant IEC 60044-2.

B FEATURES & ACCESSORIES:

a) Potential transformer shall have porcelain outdoor type bushing. b) Terminal connectors provided, shall be suitable for ACSR Merlin/ Grosbeak/ Hawk

conductor as required. c) The equipment must be tropicalized and suitable for the outdoor location. d) Galvanized nuts, bolts and all accessories required for mounting on structure shall be

provided.

e) All ferrous parts shall be hot dip galvanized after completion of machining, galvanizing shall be in accordance whether BS-729.

f) Each terminal shall have cadmium-plated nuts and bolts.

g) Each Voltage transformer is to be protected by high voltage fuse of the high rupturing capacity cartridge type. All fuses are to be clearly identified and easily accessible.

h) Diagram plate and rating nameplate shall be provided. Rating plate and diagram plate shall be made of stainless steel and have engraved letters filled with blank enamel paint mentioning manufacturer’s name, client name, year of manufacturing, contract no & model no, rating, etc.

i) Sealing/locking arrangement for the secondary terminal box shall be provided.

299

7.1.18. Technical Specification of 11KV Potential Transformer

7.1.18.1 GENERAL TECHNICAL PARTICULARS:

1. Application Metering and Protection

2. Installation Outdoor 3. Insulation Oil 4. Type Voltage Induction 5. Construction Oil Tank 6. Number of Phase Singe Phase (1Set=3Nos) 7. Frequency 50 Hz

8. Mounting Mounted Supporting on Gantry Structure Mounted 9. System Primary Rated Voltage 11 kV (Phase to Phase) 10. System Primary Maximum Voltage 12kV (Phase to Phase) 11. System Earthlings Effectively earthed 12. Basic Insulation (Impulse withstand

Voltage) 75 kV

13. Power Frequency Withstand Voltage 28 kV 14. The neutral end of primary winding, for

direct Insulated to withstand the 10 kV

connection to ground low frequency test.

15. Type of Secondary Winding Double Winding 16. Transformation Ratio (11/√3)/ (0.11/√3)/ (0.11/√3) kV

17. Creepage Distance 25 mm/ kV (minimum) 18. Rated Secondary Burden 30 VA 19. Voltage limit factor 1.2 continuous 20. Class of Accuracy 0.2 for metering and 3P for protection. 21. Standard Design, Manufacture, Testing, Installation

and Performance shall be in accordance to the latest editions of the relevant IEC 60044-2.

B FEATURES & ACCESSORIES:

a) Potential transformer shall have porcelain outdoor type bushing.

b) Terminal connectors provided, shall be suitable for ACSR Merlin/ Grosbeak/

Hawk conductor as required.

c) The equipment must be tropicalized and suitable for the outdoor location.

d) Galvanized nuts, bolts and all accessories required for mounting on structure

shall be provided.

e) All ferrous parts shall be hot dip galvanized after completion of machining,

galvanizing shall be in accordance whether BS-729.

f) Each terminal shall have cadmium-plated nuts and bolts.

g) Diagram plate and rating nameplate shall be provided. Rating plate and diagram

plate shall be made of stainless steel and have engraved letters filled with blank

enamel paint mentioning manufacturer’s name, client name, year of

manufacturing, contract no & model no, rating, etc.

300

7.1.19 Technical Specification of 33 KV SINGLE PHASE LIGHTNING ARRESTER

1 Application

Distribution Transformer/ Line/ Cable protection/ Power Transforemr of heavy duty class.

2 Type of Arrester Station Class Metal Oxide (ZnO), Gapless 3

Construction Single Unit, basically consisting of gapless hermetically sealed in with non-linear characteristics with high energy capacity, all enclosed in porcelain housing.

4 Installation Outdoor 5 Mounting Pole Mounted steel bracket 6 Nominal System Voltage 33 kV 7 Maximum continuous operating Voltage 36 kV 8 System Frequency 50 Hz 9 Number of Phase 1⌽

10 Rated Arrester Voltage 36KV 11 Continuous Operating Voltage 30 kV 12 Nominal Discharge Current

(KAp) of 8/20 micro second wave

10 KA

13 Power Frequency withstands voltage of Lightning Arrester Housing, Dry & Wet.

70 kV (Dry & wet)

14 Impulse Withstand Voltage of Lightning Arrester Housing.

170 kV (peak)

15 Lightning Impulse Residual Voltage (8/20 micro-second wave)

170 kV (peak)

16 Basic Insulation level 170KV 17 Steep Current Impulse Residual Voltage

at 10KA of 1 micro-second front time. 40 kV (peak)

18 High Current Impulse Withstand Value (4/10 micro-second)

Minimum 100 KA

19 Minimum Energy Discharge capability (KJ/KV) at rated voltage.

5

20 Temporary over voltage withstand capability (KVrms) for 10.0 secs

42KV

21 Creepage distance (minimum) 25 mm/ kV 22 Partial Discharge(pico-coulomb) when

energized at 1.05 times its continuous operating voltage.

Not exceeding 10 PC

23 Earthing system earth with earthing transformer 24 system Fault level 25KA for 3sec 25 Standard Performance, Design & Testing shall be in

accordance to IEC-6099-4/ ANSI- C 62.11 or equivalent international Standards unless otherwise specified herein.

B. FEATURES :

- The Arrester shall be Zno type, basically consisting of gapless hermetically sealed in with non-liner volt-ampere characteristics with high-energy capacity. The Earthing terminal with clamp shall be suitable to accommodate AAC/ACSR/Copper conductor of diameter from 14.1mm to 18.5mm.

301

- Terminal connectors shall be suitable for ACSR Merlin/ Gross Beak/ HAWK conductor as required.

- Zno Arrester shall be excellent thermal stability for high-energy surges, external pollution & temporary over voltage.

- Operation counter on each unit shall be provided to indicate number of operation on account of lightning of switching surges.

- Identification marks on each separately housed unit shall be provided to enable it to be replaced in current position after a multi-unit Arrester has been dismantled.

- All ferrous parts exposed to atmosphere shall be cadmium plated. - Each Arrester shall have lattice type steel, structures & shall be of sufficient high to co-

ordinate with the sub-station equipment/material supplied. Each support shall be complete in all respect.

- Arresters shall be housed in porcelain containers sealed against the entry of moisture and oxygen and free of influence of moisture and weather condition.

- Each single pole Arrester shall be furnished with a rating plate; the elements shall also have an individual rating plate. The rating plate shall indicate the main characteristics of the Arrester and must permit easy ordering of spare parts units; the rating plate making shall be in English.

- The height of the lightning Arresters and supports shall be coordinated with associated sub-station equipment.

- The connecting cable (connecting lead) from LA to surge monitor shall be provided and the connecting lead shall be insulated copper cable of minimum 16mm2 size.

- The station class surge arresters shall be complete with fittings suitable for mounting in a vertical position on mild steel channels

7.1.20 Technical Specification of 11KV SINGLE PHASE LIGHTNING ARRESTER

1. Application Transformer/ Line Protection for Sub-station of heavy-duty class.

2. Type Station type Metal Oxide (Zno) gapless.

3. Construction Single unit for mounting on steel structure.

4. Installation Outdoor. 5. System Nominal Voltage 11 KV (Phase to Phase). 6. Maximum System Voltage 12 KV 7. Power System 3-Phase, 50Hz. 8. Neutral Connection Effectively earthed. 9. Rated Arrester Voltage 12 KV (r.m.s.)

10. Rated Arrester Current 10 KA. 11. Maximum Continuous Operating Voltage 24 KV (rms) 12. Power Frequency withstand voltage of

housing

a) Dry 28 KV (rms) b) Wet 28 KV (rms) c) Impulse 70 KV (peak)

13. Lightning Impulse Residual Voltage (8/20 Micro-second front time)

32 KV (peak)

14. Steep current impulse residual voltage at 10 110 KV (peak)

302

KA of 1 micro- second front time 15. High current impulse withstand value

(4/10 micro-second) 100 KA

16. Creepage distance 25 mm (min)/KV 17. Standard Design, Manufacture, Testing,

Installation and Performance shall be in accordance to the latest editions of the relevant IEC standards.

A. FEATURES :

- The Arrester shall be Zno type, basically consisting of gapless hermetically sealed in with non-liner volt-ampere characteristics with high-energy capacity. The Earthing terminal with clamp shall be suitable to accommodate AAC/ACSR/Copper conductor of diameter from 14.1mm to 18.5mm.

- Terminal connectors shall be suitable for ACSR Merlin/ Gross Beak/ HAWK conductor as required.

- Zno Arrester shall be excellent thermal stability for high-energy surges, external pollution & temporary over voltage.

- Operation counter on each unit shall be provided to indicate number of operation on account of lightning of switching surges.

- Identification marks on each separately housed unit shall be provided to enable it to be replaced in current position after a multi-unit Arrester has been dismantled.

- All ferrous parts exposed to atmosphere shall be cadmium plated. - Each Arrester shall have lattice type steel, structures & shall be of sufficient high

to co-ordinate with the sub-station equipment/material supplied. Each support shall be complete in all respect.

- Arresters shall be housed in porcelain containers sealed against the entry of moisture and oxygen and free of influence of moisture and weather condition.

- Each single pole Arrester shall be furnished with a rating plate; the elements shall also have an individual rating plate. The rating plate shall indicate the main characteristics of the Arrester and must permit easy ordering of spare parts units; the rating plate making shall be in English.

- The height of the lightning Arresters and supports shall be coordinated with associated sub-station equipment.

- The connecting cable (connecting lead) from LA to surge monitor shall be provided and the connecting lead shall be insulated copper cable of minimum 16mm2 size.

- The station class surge arresters shall be complete with fittings suitable for mounting in a vertical position on mild steel channels

303

7.1.21 Technical Specification of Substation Battery and Battery Charger 7.1.21.1 Battery 7.1.21.1.1 General Batteries shall be located in separate mechanically ventilated rooms, which will be provided with sinks and water supplies. Storage facilities will be provided for electrolyte, distilled water and maintenance equipment. The voltage measured at the main distribution switchgear shall not vary by more than plus 10 percent or minus 20 percent of the nominal voltage under all charging conditions when operating in accordance with the requirements of this Section. The complete equipment shall preferably be a manufacturer’s standard but any departure from this Specification shall be subject to the approval of the Engineer. 7.1.21. 1.2 Type of Battery The battery shall be of the high performance Nickel Cadmium pocket plate type complying with IEC 60623 and shall be designed for a life expectancy of 25 years. Battery cases shall be of high impact translucent plastic or annealed glass and shall be indelibly marked with maximum and minimum electrolyte levels. The design of the battery shall permit the free discharge of the gases produced during the normal operating cycle, whilst excluding dust. Spray arresters shall be included. The electrolyte shall be free from impurities and the Potassium Hydroxide used shall comply with BS 5634. Dilution of the alkaline electrolyte and topping up of cells shall be carried out using distilled water only. A complete set of test and maintenance accessories, suitably boxed, shall be provided for each battery. A syringe hydrometer and a durable instruction card shall be included in each set. Cells shall be numbered consecutively and terminal cells marked to indicate polarity. Cells shall be permanently marked with the following information: - Manufacturer's reference number and code - Year and month of manufacture - Voltage and nominal capacity at the 5 hour discharge rate

The electrolyte capacity and general design of the cells shall be such that inspection and maintenance, including topping up of the electrolyte, shall be at intervals of not less than twelve months. 7.1.21.1.3 Initial Charge and Test Discharge The initial charge, test discharge and subsequent re-charge of the battery must be carried out under continuous supervision. Resistors, instruments, leads, and the other apparatus will be necessary for the initial charge, test discharge and subsequent recharge of the battery. 7.1.21.1.4 Battery Duty

304

The battery shall have sufficient capacity to supply the following continuous and intermittent loads for the periods specified, with the chargers out of service. Standing DC loading for protection, control, indications and alarms for 10 hours. This loading shall be determined from all equipment to be supplied on this Contract. In addition the future circuit requirements estimated on the same basis as the present requirements. At the end of 10 hours the battery shall have sufficient capacity to complete the operations listed below, at the end of which duty the system voltage shall not have dropped below 90 percent of the nominal voltage with the standing loads, specified above, connected. 1. Two closing operations on all circuit breakers (including future) supplied by the battery. 2. Two tripping operations on all circuit breakers (including future) supplied by the battery.

Where busbar protection is provided, it shall be assumed that all circuit breakers in any one busbar protection zone trip simultaneously.

3. Charging of DC motor wound circuit breaker closing springs (where applicable) to enable

the closing operations to be carried out. 4. At the end of these duties, the battery voltage shall not have dropped such that the voltage

at the battery terminals falls below 90% of the nominal system voltage when supplying the standing load.

5. In addition, the voltages at the terminals of all components in the system (eg. relays, trip

and closing coils) shall not be outside of the individual voltage limits applying to them. 6. A margin of 10 % shall be allowed for derating of this battery over its life time. All quantities derived in this manner shall be quoted in the Bid, but shall not be used for ordering materials until specifically approved by the Engineer. Detailed calculations, and loading characteristics on which these are based, shall be submitted to the Engineer at an early stage.

7.1.21.1.5 Location of Batteries The batteries shall be housed in a ventilated battery room. The charging equipment and distribution switchboards shall be housed in a separate room. The floor of the battery room shall be coated with a suitable electrolyte resistant protective coating. The floor shall be fitted with a drain and shall have sufficient slope to prevent any major electrolyte spillages from entering into other areas. No ducts or any other items shall penetrate the floor or create a means whereby spillage can drain away apart from the drain provided for this purpose. The ventilation fans and lamps in battery room shall be an explosion proof type. 7.1. 37.1.6 Battery mounting connections and accessories Batteries shall be placed on timber boards mounted in double tiers on steel stands of robust construction and treated with acid resisting enamel or gloss paint to BS 381C No.361. The cells shall be arranged so that each cell is readily accessible for inspection and maintenance and it

305

shall be possible to remove any one cell without disturbing the remaining cells. The stands shall be mounted on insulators and be so dimensioned that the bottom of the lower tier is not less than 300mm above the floor. Alternatively, batteries may be mounted in a similar manner on treated hardwood stands. Batteries shall be supplied and erected complete with all necessary connections and cabling. Connections between tiers, between end cells and between porcelain wall bushings shall be by PVC cables arranged on suitable racking or supports. Before jointing, joint faces shall be bright metal, free from dirt, and shall be protected by a coating of petroleum jelly. Terminal and intercell connections shall be of high conductivity corrosion free material. Cartridge fuses shall be provided in both positive and negative leads, positioned as close to the battery as possible and shall be rated for at least three times the maximum battery discharge current at the highest operating voltage. The two fuses shall be mounted on opposite ends of the battery stand or rack in an approved manner. These fuse links shall comply with BS 88 Clause DC. 40 and shall be bolted in position without carriers. Warning labels shall be fitted to warn personnel of the danger of removing or replacing a fuse whilst the load is connected and that fuses should not be removed immediately following boost charge due to the possible ignition of hydrogen gas. Fuses between the battery and charger shall be located adjacent to the battery in a similar manner to that described above. A warning label shall be placed on the charging equipment indicating the location of these fuses and the fact that they should be removed to isolate the charger from the battery. It shall not be possible to leave the battery disconnected (by means of switches or removal or operation of fuses) without some local and remote indication that such a state exists. One set of miscellaneous equipment, including two syringe hydrometers, one cell-testing voltmeter, two cell-bridging connectors, two electrolyte-pouring funnels, two electrolyte thermometers, battery instruction card for wall mounting, electrolyte airtight containers, labels, tools and other items necessary for the erection and correct functioning and maintenance of the equipment, shall be provided for each station. 7.1.22 Battery Charger 7.1.22.1 General: Each battery charging equipment shall comply with the requirements of BS 4417 (IEC 146), shall be of the thyristor controlled automatic constant voltage type with current limit facilities and shall be suitable for supplying the normal constant load, at the same time maintaining the battery to which it is connected in a fully charged condition. All equipment shall be naturally ventilated. All the equipment for each charger shall be contained in a separate ventilated steel cubicle. The charger cubicles shall normally be mounted immediately adjacent to the DC distribution panel to form a board and shall be of matching design colour and appearance. Where their ratings permit, chargers shall preferably be designed for operation from a single-phase AC auxiliary supply with a nominal voltage of 230 V. Otherwise a three phase 400V supply may be utilised. Chargers shall maintain the float charge automatically for all DC loads

306

between 0 and 100%, irrespective of variations in the voltage of the ac supply within the following limits : - Frequency variation : 47 to 51 Hz. - Voltage variation : ± 15% The mains transformer shall be of a suitable rating and design. Clearly marked off-circuit tappings shall be provided on the primary windings and change of tapping shall be by means of easily accessible links. The transformer shall be of the natural air-cooled type capable of operating continuously at full load on any tapping with the maximum specified ambient temperature. All rectifiers and semi-conducting devices employed in the charger shall be of the silicon type. They shall be adequately rated, with due regard to air temperature within the charger enclosure, for the maximum ambient temperature. The rating of the charger on float charge shall be equal to the normal battery standing load plus the recommended finishing charge rate for the battery. Each charger shall also incorporate a boost charge feature which shall, after having been started, provide an automatically controlled high charge rate sufficient to restore a fully discharged battery to the fully charged state within the shortest possible time without excessive gassing or any form of damage to the battery. The boost charge shall be initiated manually or automatically upon detection of a significant battery discharge. An adjustable timer shall be provided to automatically switch the charger to the float condition after the correct recharge period. Should the AC supply fail while a battery is on boost charge, the switching arrangements shall automatically revert the charger to float charge status and then reconnect the battery to the distribution board. The output voltage regulator shall be adjustable for both float and boost charge modes, within limits approved by the Engineer, by means of clearly marked controls located inside the cubicle. Although it is not intended that the charger be operated with the battery disconnected, the design of the charger shall be such that with the battery disconnected the charger will maintain the system voltage without any damage to itself and with a ripple voltage no greater than 2.0% rms of the nominal output voltage. The charger shall automatically adjust the charging current from a value not less than the battery capacity divided by 10 hours to a minimum value of not more than the battery capacity divided by 200 hours. The charging circuitry shall be so designed that the failure of any component will not give a situation which will cause permanent damage to the battery by over charging. Each charger shall have a float charge maximum current rating sufficient to meet the total standing load current on the dc distribution board plus a battery charging current equal numerically to 7% of the battery capacity at the 10 hour rate. Each charger shall be designed with a performance on float charge such that with the output voltage set at approximately 1.45 V per cell at 50% load and rated input voltage and frequency, the output voltage shall not vary by more than plus 3% to minus 2% with any combination of input supply voltage and frequency variation as stipulated in this Specification and output current variation from 0-100% of rating.

307

Each charger shall be suitable for operating alone or in parallel with the other charger. When operating with both chargers, one charger shall be arranged to supply the standing load with the second charger in the quiescent standby mode. Each charger shall also have a taper characteristic boost charging facility which shall be selectable by a float/boost charge selection switch and which will give boost charging of 1.60 volts per cell. Each charger shall be designed with a performance on boost charge such that with rated input voltage and frequency the charger output shall not be less than its rating in Watts at 1.3 V and 1.6 V per cell, and also the output voltage shall be 1.60 per cell over an output range of 0 - 100% of rating. The boost charging equipment shall be capable of recharging the battery within six hours following a one hour discharge period. In the event of the battery becoming discharged during an AC supply failure, the rate at which recharging commences shall be as high as possible consistent with maintaining the automatic charging constant voltage feature and with the connections remaining undisturbed as for normal service. The charger shall have an automatic boost/quick charge feature, which shall operate upon detection of a significant battery discharge. When, after a mains failure, the AC supply voltage returns and the battery have been significantly discharged, the charger will operate in current limit. If the current limit lasts for more than a specified time and the charging current does not fall back to float level, the automatic high rate charge shall be activated. An override selector switch shall be provided inside the charger unit to enable a first conditioning charge to be made, in line with the battery manufacturer’s recommendations, for batteries which are shipped dry and require forming at site. A blocking diode unit shall be incorporated in the output circuit of each charger to limit the load voltage during boost charging of the battery. The diode unit shall not be in service in the normal float charging mode. Should the stabiliser fail in the boost charging mode, the charger shall automatically revert to the float mode. An anti-parallelling diode shall be provided in each positive feed to the DC distribution board to prevent faults on one supply affecting the other. These diodes shall be continuously rated to carry the maximum possible discharge current likely to occur in service and a safety factor of 4 shall be used to determine the repetitive peak reverse voltage rating. The I2t rating of the diodes shall be such that in the event of a DC short circuit, no damage to the diodes shall result. Each charger shall be capable of sustaining, without damage to itself, a continuous permanent short circuit across its output terminals. The use of fuses, MCBs or other similar devices will not be acceptable in meeting this requirement. Suitable relays shall be provided for each charger to detect failure of the incoming supply and failure of the DC output when in float charge mode. These relays shall operate appropriate indicating lamps on the respective charger front panel and shall have additional voltage free contacts for operating remote and supervisory alarms. These alarms shall be immune from normal supply fluctuations and shall not be initiated when any one charger is taken out of service.

308

The charger shall also be fitted with a device to de-energise the charger in the event of a DC output float over voltage. Each charger shall be provided, as a minimum, with the following instrumentation, indication and alarm facilities:- -Indicating lamps for the AC supply to the rectifier and DC supply from the rectifier. - Indicating lamps for float and boost charging operations. - Voltmeter - Input voltage. - Voltmeter - Output voltage. - Ammeter - Output current. - Alarm - Charger failure. - Alarm - Mains failure. The following battery alarms shall also be provided: - Battery fuse failure - Diode assembly failure - Battery circuit faulty - Low DC volts - High AC volts - Earth fault +ve - Earth fault -ve Lamp test facilities shall be included. A “charger faulty” alarm for each charger and a “battery faulty” alarm shall be provided in the substation control room and to the SCADA system where applicable. Each battery charger shall be equipped with charge fail detection equipment to give local indication and remote alarm if the voltage from the charger falls below a preset level which will be lower than the nominal float charge voltage. Suitable blocking diodes shall be provided to prevent the battery voltage being supplied to the equipment and so prevent charge fail detection. The device shall not operate on switching surges or transient loss of voltage due to faults on the AC system. The voltage at which the alarm operates shall be adjustable for operation over a range to be approved by the Engineer. Each charger shall be equipped with a switch-fuse for the incoming AC supply and an off load isolator for the DC output. Bidders shall include particulars with their Bid on the method of adjustment included to compensate for ageing rectifier elements. The construction of the charger shall be such that access to all components is readily available for maintenance removal or replacement. Internal panels used for mounting equipment shall be on swing frames to allow for access to the charger interior.

7.1.22.2 Earthing Screen Earthed screens shall be provided to protect the equipment from direct lightning strikes. The screens shall be of aluminium clad steel wires of not less than 50 sq.mm. total section, and connected to provide low impedance paths to earth.

309

The layout of the earth wires shall be such that equipment to be protected generally lies within areas bounded by two or more conductors, in which case the protected angle shall not exceed 45 degree centigrade. Where equipment is protected by a single earth wire, the protective angle shall not exceed 35 degree centigrade to the vertical. The earth screens shall be suitable for extension to protect the substation equipment to be installed in future stages of development. Connections shall be made of copper strip of 30mm x 5mm cross section between the overhead earthed screen wire and the main substation earthing system at each support unless the galvanized steel support structure has sufficient area and current carrying capacity. Earth wires shall be held in clamps with free pin type joints between clamps and supports. Connections shall be provided for the terminations of the earth wires of the overhead lines, including bimetal connectors where necessary. The design of all structures shall generally comply with the specification and in addition is to ensure that in the event of breakage of one earth wire, the Factor of Safety is not less than 1.5. 7.1.23 GROUNDING MATERIAL The grounding wire shall be 125mm2 stranded copper conductor. All nuts & bolts shall be cadmium plated. The washers shall be sine plated. All clamps contort shall be of 25mmx 4mm copper. All clamps connectors shall be of quality manufacturer such as Burnaby or equal. Connector to equipment shall be by bare copper cable/flexible copper braid as required. The grounding copper electrode shall be 16 mm Dia. And each 4 meter length. 7.1.24 TECHNICAL SPECIFICATIONS 33kV DISC INSULATOR WITH FITTINGS 7.1.24.1 STANDARDS:

These 33 kV Disc Insulator with Fittings specified in this Section shallconform to the latest edition of the following standards for operation in overhead lines in air under local ambient conditions. Design, Manufacture, Testing and Performance shall be in accordance with latest revisions of BS, IEC standards as listed below or other equivalent internationally acceptable Standards: IEC-120 : Ball & Socket Coupling. IEC-305 : Characteristics of String Insulator Unit. IEC-383 : Insulator Tests. IEC-437 : Radio Interference Tests. IEC-506 : Switching Impulse Tests. IEC-575 : Thermal Mechanical Performance Tests. BS-137 : Method of test & requirements. BS-916 : Bolts, Screws & Nuts.

7.1.24.2 SPECIFICATIONS:

310

A. Specification of Disc Insulator:

These 33 kV Disc Insulators shall be designed as per above standards for operation in overhead lines in air under local ambient conditions.

1. Installation Overhead line for suspension or termination.

2. Nominal System Voltage, kV 33 (line to line). 3. Type of System Three phase, 50 Hz, Three Wire,

Effectively earthed. 4. Highest System Voltage, kV 36 (three phase). 5. Atmospheric Condition Moderately polluted. 6. Altitude, meter 0-300 above sea level. 7. Maximum Ambient Temperature, ºC

45.

8. Insulator Material The Insulator shall be made of good commercial grade wet process porcelain. The porcelain shall be sound, thoroughly vitrified and free from defects and blemishes that might adversely affect the life of the Insulator. The exposed parts of the porcelain shall be smoothly glazed and shall be brown in color unless otherwise specified.

9. Type of Insulator

Ball & Socket type Disc, security clip made of Stainless Steel or Phosphor Bronze.

10. Markings

Each Insulator shall be marked with the name of Trade Mark of the manufacturer, the type of Insulator and the year of manufacture. These markings shall be legible and indelible.

11. Maximum Nominal Diameter of Insulator, mm

255

12. Nominal Spacing, mm 146 13.

Minimum Nominal Creepage Distance, mm

292

14. Coupling Size, mm 16 15. 15.1 15.2 15.3

WITHSTAND VOLTAGE, MINIMUM Power Frequency, dry (one minute), kV Power Frequency, wet (one minute), kV Impulse 1.2x50 micro-sec wave, kV

70 40 110

16. FLASHOVER VOLTAGE, MINIMUM

311

16.1 16.2 16.3 16.4

Power Frequency, dry, kV Power Frequency, wet, kV 50% Impulse 1.2x50 micro-sec wave, positive, kV 50% Impulse 1.2x50 micro-sec wave, negative, kV

78 45 120 125

17. POWER FREQUENCY PUNCTURE

VOLTAGE MINIMUM, kV

110

18. 18.1 18.2

RADIO-INFLUENCE VOLTAGE DATA MINIMUM: Power Frequency Test Voltage, RMS to Ground, kV Maximum RIV at 1000 KC Micro-volt

10 50

19. MECHANICAL FAILING LOAD MINIMUM, kN

70

B. Specification of 33 kV Strain Insulator String Set:

33 KV Strain Insulator String Set consisting of the following component parts for each set. Design, Manufacture, Testing and Performance shall be in accordance with latest revisions of BS-3288 or other equivalent internationally acceptable Standards.

1. Anchor Shackle

Made of forged steel galvanized complete with cotter bolt and Pin, UTS-6800 Kg, Galvanization as per BS-729 OR ASTM A-153 part 1 or ASTM A-153.

2. Ball Eye Oval eye type, made of forged steel galvanized, UTS-6800 Kg, Galvanization as per BS- 729 part 1 or ASTM A-153.

3. Socket Eye Made of malleable iron galvanized complete with cotter bolt and Pin, UTS-6800 Kg, Galvanization as per BS- 729 part 1 or ASTM A-153.

4. Strain Clamp

Bolted type, Made of malleable iron galvanized or Alluminium Alloy, suitable for accommodating ACSR GROSBEAK of overall diameter 25.15 mm, complete with bolts, nuts, washers, Alluminium Alloy liner etc., UTS-6800 Kg, Galvanization as per BS- 729 part 1 or ASTM A-153 in case of malleable iron or other ferrous metal.

5. Disc Insulator 3 (Three) Nos. are required for each set.

7.1.25 H-Type Connectors 7.1. 40.1 STANDARDS:

The H-Type Connectors as specif ied in this Section shallconform to the latest edition of the following standards for operation in overhead lines in air under local ambient conditions. Design, Manufacture, Testing and Performance of the H-Type

312

Connector shall be in accordance with the BS-3288 Part-1 &BS-4579 Part 3 or equivalent International standards.

7.1. 40.2 SPECIFICATIONS:

The H-Type Connectors will be used for connecting the ACSR Conductors to ACSR Conductors, AAC Conductors to AAC Conductors and Copper Conductors to AAC conductors. These should be Uni-metal or Bi-metal type according to the contractions and applications of such connectors. These should be made from high conductivity Aluminium and pre-filled with oxide inhabiting compound. The design of the compression type connectors should be such that galvanic corrosion is minimised. Conductor rough & tooling shall be clearly joined on the connectors. The connector must have at least the same conductance as the conductor for which it is intended to be used and shall carry the full continuous current rating of the conductor size they are designed for. The original quality of contacts shall be maintained through out the service life of the connectors. Glow discharge and radio interference must be reduced to a minimum level.All compression type connectors shall be suitable for installation, using either manual or hydraulic compression tools.

The size of the connectors for different Conductors is as follows:

Grove A Grove B

Max (mm2)

Min (mm2)

Max (mm2)

Min (mm2)

Length in mm

ACSR GROSBEAK/ACSR GROSBEAK

400 350 400 350 150.00

ACSR MERLIN/ACSR MERLIN

185 150 185 150 112.00

ACSR DOG/ ACSR DOG 120 95 120 95 63.00

AAC WASP/ AAC WASP 120 95 120 95 63.00

AAC ANT/ AAC ANT 70 50 70 50 47.00 AAC WASP / Service Bail 120 95 35 16 63.00

AAC ANT /Service Bail 70 50 35 16 47.00

7.1.26 SHIELD WIRES:

1. Installation Sub-station 2. Type Stranded 3. Material High Strength Steel 4. Nominal Size 9.525 mm 5. Number of Strand 7 (Seven)

313

6. Diameter of Each Strand 3.05 mm 7. Overall Diameter 9.525 mm 8. Weight per KM Length 407 Kg 9. Rated Ultimate Tensile Strength 4,900 Kg/mm2

10. Class of Zinc Coating Class-A 11. Galvanization As per BS-729 OR ASTM A-153 12. Grade of Steel 60,000 Kg 14. Standard Design, Manufacture, Testing, Installation and

Performance shall be in accordance to the latest editions of the relevant IEC standards.

A. FEATURES

- Wires shall be shipped on standard non-returnable wooden reels Gross weight shall not exceed 800 Kg per reel. The minimum length of wire per reel shall be 1500 M.

- Each reel shall have the following information stenciled on side size and kind of conductor, length of conductor, gross and net weight. No joints of any kind shall be made in the finished wire entering into the construction of strand.

- The diameter of each zinc coated wire forming the strand shall not differ from the diameter specified by more than plus or minus 0.01 mm.

- The strand shall have a left hand lay with a uniform pitch of not more than 16 times the normal dia. of the strand.

B. PACKING AND SHIPPING

Grounding wire reels shall be constructed sufficiently strong to withstand usual requirement shipping, transporting and field erection.

C. HARDWARE FOR SHIELD WIRE

i) Angular 900 bolted type T-connector of malleable iron galvanized steel or aluminum alloy suitable for 9.525 mm dia, 7/3.05 mm stranded high strength galvanized steel wire run to 9.525 diameter, 7/3.05 mm stranded high strength galvanized steel wire tap.

ii) Angular 450 bolted type clamp made of aluminum alloy suitable for 9.525 mm diameter,

7/3.05 mm stranded high strength galvanized steel wire run to 9.525 mm diameter 7/3.05 mm stranded galvanized steel wire tap.

iii) Shield wire clamp set suitable for 9.525 mm diameter 7/3.05mm stranded high strength

galvanized steel wire, comprising of the followings :

a) Bolted wire strain clamp made of malleable iron galvanized steel or aluminum alloy complete with nuts bolts washers etc. anchor shackle made of forged steel galvanized complete with cotter bolt and pins.

b) Double eye rectangular made of forget galvanized. c) Wire clip made of malleable iron galvanized or aluminum alloy.

7.1.27 PG Clamp:

STANDARDS:

The PG Clamps as specif ied in this Section shal lconform to the latest edit ion of the following standards for operation in overhead lines in air under local ambient conditions. Design, Manufacture, Testing and Performance of the PG Clamp

314

shall be in accordance with the BS-3288 Part-1 &BS-4579 Part 3 or equivalent International standards.

SPECIFICATIONS:

The PG Clamps will be used for connecting the ACSR Conductors to ACSR Conductors and AAC Conductors to AAC Conductors. Parallel Groove Clamp, a non tension bolted type connector, shall be made of Aluminium Alloy, massively designed body. The bolts are made of Galvanised Steel. For the insulated conductors, 0.80 mm thick PVC insulation cover is to be provided with full length clamp. The clamps must have at least the same conductance as the conductor for which it is intended to be used and shall carry the full continuous current rating of the conductor size they are designed for. The original quality of contacts shall be maintained through out the service life of the clamps. Glow discharge and radio interference must be reduced to a minimum level. The size of the connectors for different Clamps is as follows:

7.1.28 LV AC Distribution Panel Vermin and dust proof, completely metal enclosed by sheet steel (11 SWG) with necessary reinforcement, colour, Grey with appropriate spray painting, free standing type, compact in size, suitable for opening at the back by hinged door with locking device. There shall be a 3 phase 400 A, 1 KV bus (Cu) arrangement with neutral. Bus being connected with the following MCCB's and instrument. : Voltmeter with 6-position selector switch connected to the bus. 2 400A, 4 pole MCCB being interlocked with each other, operative one at a time to bring the input Power to the Bus. Both these incoming feeders shall have 3 x ammeter (each). 2 100A, 3 pole MCCB as outgoing. 10 60A, 3 pole MCCB as outgoing.

Conductor Size

(sq. mm)

Conductor Diameter

(mm)

Dimension No. of Bolt L

(mm) W

(mm) ACSR GROSBEAK, either side

370 25.15 125 50 3

ACSR MERLIN, either side

170 17.35 110 45 3

ACSR DOG, either side

100 14.15 95 30 2

ACSR RABBIT, either side

50 10.05 80 22 2

AAC WASP, either side

100 13.17 95 30 2

315

10 30A, 3 pole MCCB as outgoing. The Short Circuit Current rating of each 3 phase MCB and MCCB shall be of at least 36 kA and that for 1 phase shall be at least 10 kA. All MCCB's are provided with over load setting and short circuit tripping device. There shall be a 3-φ 4-wire class 0.5 energy meter for recording the station use. Necessary terminal blocks and glands/openings shall be provided for the entry of suitable cables. All equipment/instruments inside the panel shall be arranged neatly and sufficient space shall be provided for easy approach to each equipment/instrument. Thermostat controled panel heater, bulb for inside illumination of panel shall be provided. All other features as stated in the table of guaranteed data schedule shall applicable also. 7.1.29 DC Distribution Panel The switchboard shall comply with the requirements of BS 5468 (IEC 60439) The distribution switchboard shall be of the cubicle type or otherwise incorporated in the cubicles for battery chargers. Double pole switches and fuses or switch fuses (miniature circuit breakers to BS 4752 or IEC 60127 may only be used if it can be shown that there will be no discrimination problems with sub-circuits) shall be fitted to the DC switchboard as required by substation services but, as a minimum requirement, that set out in the Schedule A of Requirements. Distribution panels shall be mounted adjacent to the charger control panel and shall be of the cubicle type complying with the general requirements of cubicle type control panels. No equipment associated with the chargers shall be installed in the distribution board. Distribution panels shall incorporate double-pole switches for each of the outgoing DC circuits and double-pole isolators for the incoming DC supplies. The panel shall be provided with a voltmeter and centre zero ammeter on each incoming circuit. A double pole switch or contactor shall be provided for the purpose of sectionalising the busbar. A battery earth fault detecting relay, which will centre tap the system via a high resistance, shall be incorporated in the distribution panel. A low voltage detecting device for the system shall be incorporated in the distribution panel. No-volt relays will not be accepted for these devices. The voltage setting shall be adjustable over an approved range. In addition to any other requirements specified elsewhere, the battery earth fault detecting relays and low voltage devices shall each have three alarm contacts, one for local visual annunciation, one for the station control panel alarm indication and one for potential free contact for external supervisory alarms. A lamp test facility shall be provided.

316

Connections between the battery and the distribution cubicle shall be made in PVC insulated cable as required. Cable laid in runs where it may be subject to damage shall be protected by wire armouring, be sheathed overall and be cleated to walls as required. Cable boxes or glands shall be provided as appropriate for all incoming and outgoing circuits of the distribution switchboard and associated battery chargers. Each circuit shall be suitably labelled at the front of the panel and at the cable termination where the terminals shall be additionally identified. Charging and distribution switchboards shall be provided with an earthing bar of hard drawn high conductivity copper which shall be sized to carry the prospective earth fault current without damage or danger. The cubicles for the chargers and distribution boards shall be of rigid, formed sheet metal construction, insect and vermin proof, having front facing doors allowing maximum access to the working parts, when open. The design of the cubicles for the chargers shall be such as to prevent the ingress of dust and minimise the spread of flames or ionised zones, shall be to IEC 60529 IP52, but at the same time shall provide all necessary ventilation and cooling. The design of the frames shall allow the clamping and holding of all chokes, transformers and similar sources of vibration, so that vibration will be minimised, satisfy relevant standards, and not limit the life of the equipment. The frame shall allow the fixing of lifting and so that the equipment remains properly mechanically supported whilst being transported, lifted and installed. 7.1.30 Sub-Station Steel Structure

GENERAL

The structural steel shall conform to the latest provision of ASTM A36/BS-4360 and all the parts shall be hot dip galvanized as per BS-729 after fabrication.

SCOPE

The work covered by these specifications shall include design, fabrication, marking, painting, galvanizing, supply of all materials, suitable for the location, sea worthy packing, transportation to S/S site, storage on the site, site visit needed to complete the sub-station structures, miscellaneous steel members, nuts, bolts, plates etc. according to specifications and drawings prepared by the bidder and approved by the Purchaser.

DESIGN DATA

Structure shall be designed on the basis of the following:

i) Buses, structures, conductors and shield wires shall be designed to withstand the force

of a true wind velocity of 160 KM per hour (120 kg/m2 on round surface, 200 KG/m2 on flat surface). The over load capacity factor shall be 2.

ii) All connections between steel members shall be bolted, minor welds will be allowed for

fabrication purposes before galvanization, but no welding will be permitted in the main legs of members of terminal structure. The diagonals and struts shall be bolted directly to the structure legs and to each other. Gasket plats shall not be used unless absolutely necessary.

Members shall be design to avoid depressions that can trap water, such depressions if

317

unavoidable, shall have drain holes, and connections shall be designed so that all bolts can be tightened in the field using a flat erection wrench. The ends of connected members, shall, where necessary, be clipped or cut to allow free movement of the wrench.

The quantity of bolts, nuts and locking devices furnished shall include the number of each size required for erection plus an additional 5% of that number to cover loss and damages.

The bus supports shall be designed to withstand a momentary short circuit current equal to the momentary short circuit rating of the associated breakers.

All shield wires for the sub-station shall be 9.525 mm dia 7 strands with high strength steel galvanized wire.

The contractor must supply complete detailed drawings, bill of materials, composition of materials etc. all connectors, clamps, fittings, hardware, etc. with their range of adjustment. Detailed catalogues, printed literatures etc. showing all significant characteristics for all those things for which the contractor intends to offer must be supplied with the offer. Particular items proposed to be supplied, must be arrow marked in the catalogue.

Material

All materials used for the sub-station structures and buses shall be new and undamaged and shall conform to the requirements given below certified test reports for all steel materials shall be submitted to the Engineer before such materials shall be fabricated. The latest revisions to the specified American Society for Testing Materials (ASTM) and General Specifications ruling.

i) STEEL STRUCTURE MEMBER

The main steel structure shall be designed for the loading specified and separate additional structures as necessary shall be provided for overhead line terminations, disconnect switches, bus supports, potential devices lightning Arresters and other equipment.

The structures steel shall conform to the latest revision of ASTM for “Steel Bridge and Buildings” or equivalent and all parts shall be hot dip galvanized after packing for fabrication.

All structures shall be shipped completely unassembled unless other-wise specified. All S/S parts shall be plainly marked as aid in assembly and the marking shall agree with the identification on the erection drawings.

The structures shall be completed with all bolts, nuts and locking devices which are required for erection of the structures and for installation of equipment.

ii) CONNECTION FASTENERS

All connections shall be made with hot dip galvanized, sodium carbon, heat treated, regular square head, bolts to meet Feb Spec FF-B-575. Type-1, Grade-5 or of equivalent standard with hot dip galvanized, heavy semi finished hexagonal nuts. Each fastener shall gave a locking devices by screw and bolt, length of which shall provide 3mm (minimum) to 12.5 mm (maximum) projection beyond nut when connection is tightened. Standard ASTM-A 394 or equivalent.

iii) WELDING ELECTRODE

Where welding is permitted in Fabrication it shall be done in accordance with ASTM

318

specification A233 using F-70 series low hydrogen electrode as recommended by American Welding Society (AWS) or equivalent for various grades of steel.

iv) GALVANIZED COATING

All angles, channels, plates and other shaped or members required for these structures shall be galvanized in accordance with ASTM specification A123 or equivalent. Galvanizing is to be applied on after fabrication is competed as per BS-729 (1971) Galvanization shall be done when fabrication is complete.

VI) GROUND CONNECTION

Grounding will be done by placing a copper wire/bar Grid having cross section not less then 150 mm2. Earthing rods/electrodes of copper having minimum diameter of 150 mm shall be inserted deep into soil and jointing/welding the rod with the grid as well as earthing electrodes shall be designed in such a way that Grounding resistance requirement is achieved as per IEEE 80 considering 25 kA fault current. All the joints within the grounding grid will be cad welding type. Existing grounding is to be upgraded in accordance with the new higher size power transformer.

The size/type of earthing leads for different equipment shall be as follows :

1 Neutral of the power transformer, 33/11 KV, 10/13 MVA

-not less than 240mm2 copper conductor/bar with adequate insulation

2 Body of the power transformer, 33/11 KV, 10/13MVA

- bare copper bar of not less than 2x120mm2

3 Neutral of the station transformer, 33/0.4 KV

- not less than 120 mm2 PVC LT cable

4 Body of the station transformer, 33/0.4 KV - not less than 120 mm2 Cu wire

5 33 KV PT LV Neutral - 16 mm2 Cu. Wire.

6 11 KV PT LV Neutral - 16 mm2 Cu wire

7 Steel mounting structure at the switchyard - 120 mm2 Cu wire

8 Body of the indoor 33 KV switchgear Panel - not less than 3x120 mm2 Cu wire

9 Body of the indoor 11 KV switchyard Panel - not less than 4x120 mm2 Cu wire

10 Body of the Indoor control relay panel - 33/11 KV A.C. distribution panel. DC distribution panel, battery charger and other miscellaneous indoor equipment.

- 120 mm2 Cu wire

11 33 KV Lightning Arrestor Outdoor - not less than 120 mm2 Cu wire

The earthing leads with appropriate thimble shall be connected to the welded flat bar earth electrode, by bolts & nuts.

The other ends of the earthing leads shall be connected to the equipment/chassis at appropriate terminals by using thimbles/connectors etc and nuts & bolts.

Earthing Device

Appropriate earthing devices and arrangement shall be provided for all 33KV and 11KV switching panels having provision for operation from the front.

319

FABRICATION

The Purchaser/ Engineer shall be notified when fabrication of the materials is to begging so that Owner/ Engineer may, if desires, provide shop inspection.

Each steel component shall be completely fabricated and then galvanized in the shop. All workmanship and finishing shall be first class and equal to the best practices in modern steel fabricating shops. All angles and members shall be fabricated in accordance with the standard, specifications and details given in the edition of the “Steel Construction Hand-Book” issued by the American Institute of Steel Construction or its equivalent. Structural item as delivered to the job site shall have all members straight, free from warp, bends or local deformations, accurate, sot that when the structure is assembled, proper fit will be provided. All reaming of holes shall be done at the factory before galvanizing. Punching, drilling or reaming of holes after galvanizing will not be permitted. Holes, 18mm in diameter shall be provided in the steel for ground connection on each leg of each structure. Legs or members shall be drilled with 18 holes at 1.5m intervals, in all of members where ground conductors are to be installed for grounding of shield wires or equipment. These holes shall be made before galvanizing. Holes shall be drilled and attachment devices shall be furnished on the terminal structures for all overhead circuit conductors and shield wires.

The bolt holes shall not exceed the diameter of the bolt by more than 1.5mm. Leg angles and other members shall be lap spliced and the back of the inside angle shall be round to clear the fillet of the outside angles. i) WELDING

All welding done in the shop on steel members shall be by the shield metal are processes using joints details performed in accordance with the American Welding Society (AWS) code or equivalent. All welding procedures and operators shall be qualified by an independent testing laboratory in accordance with AWS standard qualification procedures. Accurate records of operator and procedure qualifications shall be maintained by the contractor and shall be available to the owner or Engineer. All welds shall be continues and shall develop full strength of the least strength component unless otherwise shown on the drawings.

Components shall be thoroughly cleaned before welding and shall be accurately fitted and rightly secured in position during welding and weld surface shall be smooth and uniform and shall be thoroughly cleaned of all slag flux before galvanizing.

ii) MAKING

Each separate structure member shall be plainly stamped with a number. All like parts shall have the same number. The marking shall be stamped into the metal with figures at least 15mm high. Impression shall be made before galvanizing and have sufficient depth so that hey are plainly visible after galvanizing. The mark shall be placed as nearly as possible in the same relative position on each pieces so as to be seen plainly after assembly of the structure.

The mark numbers shall be composed of letters and numbers that will designate the S/S and type of structure. These markings shall the same as shown on the fabrication and erection drawings.

iii) GALVANZING All steel components of the structures shall be galvanized using the hot dip process. Fabrications shall be completed before galvanizing. All pieces to be galvanized shall be thoroughly cleaned to remove paint, grease, rust, scales or other materials that could interfere with the bonding of zinc with the steel. Galvanization shall be as per BS-729.

The contractor shall perform all works in accordance with the rules and requirements as specified under ASTM specifications A123, A153 and BS-729.

320

After galvanizing, steel members may be straightened, if necessary by being re-rolled or pressed only. No punching welding or any other work which may damage the protective cover shall be allowed after galvanizing, except the lapping of nuts. All holes shall be free from pelter after galvanizing.

iv) DRAWINGS The contractor shall furnish to the employer/ engineer complete fabrication and erection drawings along with the strength calculations on buses and loading on each structure foundation of each type of S/S structure for approval before fabrication. Drawings shall show outline, dimensions, drilling and details of fabrications.

F. STRUCTURE

All structures shall be designed, fabricated, galvanized etc. as specified and as described below : i) TERMINAL STRUCTURES

The “Terminal Structure” is identified as the structure on which the 11 KV services cable/overhead conductor are terminated. When designed to accept the cable termination, this shall be complete with all plates, bases and other fittings required for mounting the cable and box for 11 KV XLPE single core cable of appropriate size 2x1Cx240 Sq.mm cable per phase) with mounting switches etc.

For overload conductors and shield wires, the maximum tension per conductor shall be 450 Kg. ii) BUS SUPPORT STRUCTURES

The bus support structures shall be pedestal type, steel columns used to support the strain ACSR S/S buses. These structures shall be designed to withstand the forces outlined herein without damage off deformation. All plates and bus support insulators shall be furnished.

G. STRUCTURE FOUNDATION

The contractors shall furnish the detail design for foundations of all steel structures considering soil pressure of <4880 Kg/m2. A copy of calculations and design criteria for foundation along with complete bill of materials of sand, cement, reinforcing bar and concrete aggregate etc. shall be furnished after singing of the contract and at the time of drawing approval.

H. PACKING

i) Steel members shall be shipped unassembled only members with the same mark shall be bundled together.

ii) All packages shall be securely tied with heavy gauge annealed galvanized steel bands to withstand transportation handling.

iii) Parts shall be handled and loaded, without damaging the materials or galvanized coatings.

iv) The contractor shall replace, free charge all materials which has been damaged due to inadequate of faulty packing.

I. TAGGING

i) For erection purpose, each package or bundle shall be tagged to identify the number of pieces.

ii) For shipping purpose separate tagging shall be used for each package and bundle showing the name and number of the contract, gross weight, port of dispatch and the destination in Bangladesh.

321

7.1.31 BUS-BAR CONDUCTOR AND JUMPERS

1. Installation Sub-station, Outdoor.

2. Type Aluminum Conductor Steel Reinforced (ACSR)

3. Code Name MARTIN ACSR for Bus-Bar Gross Beak ACSR for Jumpers

4. Conductor Size 1351.5 MCM for MARTIN ACSR 636 MCM for Gross Beak (ACSR)

5. Standard Performance, design & testing shall be in accordance to the latest editions of ASTM B-232.

6. Shipment On standard non-returnable wooden reels Gross weight shall not exceed 2000 Kg per reel.

7. Standard Design, Manufacture, Testing, Installation and Performance shall be in accordance to the latest editions of the relevant IEC standards. A. FEATURES

- Shall be of continuous length between supports. - Conductors to be used for bus bars shall be stressed not more than 33% of their

breaking strength. - Overhead conductors carried by the S/S structures shall be erected with such a tension

that when the conductors are subject to a transverse wind pressure of 640 Pascal's on the whole projected area, the factor of safety is not less than 2 (Two).

- When dissimilar metals are in contact, approved means shall be provided to prevent elector-chemical action and corrosion.

7.1.32 ELECTRICAL HARDWARE FOR 33KV SWITCHYARD

- All connectors shall be compression type and made of Aluminum alloy suitable for the

conductor. - Load support clamps shall be complete with bolts, nuts, lock washers etc. complete and

of the appropriate size. - Clamps and fittings made of steel or malleable iron shall be galvanized as per BS-729. - Joints and connections shall be such as to permit easy dismantling. All necessary

terminals and connections (bi-metallic) shall be provided for connection to the equipment. Suspension and tension conductor clamps shall be as light as possible and shall be of approved type.

- Tension conductor clamps shall be not permit slipping of or damage to or failure of the complete conductor or any part, thereof at a load less than 70% of the breaking load of the conductor.

- Catalogue with making on the catalogues of the hardware proposed shall be submitted with the offer.

7.1.33 SHIELD WIRES

1. Installation Sub-station

2. Type Stranded

3. Material High Strength Steel

4. Nominal Size 9.525 mm

5. Number of Strand 7 (Seven)

6. Diameter of Each Strand 3.05 mm

7. Overall Diameter 9.525 mm

8. Weight per KM Length 407 Kg

9. Rated Ultimate Tensile Strength 4,900 Kg/mm2

10. Class of Zinc Coating Class-A

322

11. Galvanization As per BS-729

12. Grade of Steel 60,000 Kg

14. Standard Design, Manufacture, Testing, Installation and Performance shall be in accordance to the latest editions of the relevant IEC standards.

A. FEATURES

- Wires shall be shipped on standard non-returnable wooden reels Gross weight shall not exceed 800 Kg per reel. The minimum length of wire per reel shall be 1500 M.

- Each reel shall have the following information stenciled on side size and kind of conductor, length of conductor, gross and net weight. No joints of any kind shall be made in the finished wire entering into the construction of strand.

- The diameter of each zinc coated wire forming the strand shall not differ from the diameter specified by more than plus or minus 0.01 mm.

- The strand shall have a left hand lay with a uniform pitch of not more than 16 times the normal dia. of the strand.

B. PACKING AND SHIPPING

Grounding wire reels shall be constructed sufficiently strong to withstand usual requirement shipping, transporting and field erection.

C. HARDWARE FOR SHIELD WIRE

i) Angular 900 bolted type T-connector of malleable iron galvanized steel or aluminum alloy suitable for 9.525 mm dia, 7/3.05 mm stranded high strength galvanized steel wire run to 9.525 diameter, 7/3.05 mm stranded high strength galvanized steel wire tap.

ii) Angular 450 bolted type clamp made of aluminum alloy suitable for 9.525 mm

diameter, 7/3.05 mm stranded high strength galvanized steel wire run to 9.525 mm diameter 7/3.05 mm stranded galvanized steel wire tap.

iii) Shield wire clamp set suitable for 9.525 mm diameter 7/3.05mm stranded high

strength galvanized steel wire, comprising of the followings :

a) Bolted wire strain clamp made of malleable iron galvanized steel or

aluminum alloy complete with nuts bolts washers etc. anchor shackle made of forged steel galvanized complete with cotter bolt and pins.

b) Double eye rectangular made of forget galvanized. c) Wire clip made of malleable iron galvanized or aluminum alloy.

7.1.34 SUB-STATION EARTHING A. SCOPE

These Clauses describe the General Requirements for the Earthing and Lightning Protection and shall be read in conjunction with the Project Requirements and Schedules.

B. REFERENCES

American Standards

323

ANSI/IEEE std 80 : IEEE Guide for Safety in AC Substation Grounding

ANSI/IEEE std 81 : IEEE Guide for Measuring Earth Resistivity, Ground Impedance,

and Earth Surface Potential of a Grounding System.

German Standards

DIN VDE 0141 : Earthing Systems for Power Installations with Rated Voltages

above 1 KV.

British Standards

BS 1432 : Specification for copper for electrical purposes; high conductivity

copper rectangular conductors withdrawn or rolled edges.

BS 1433 : Specification for copper for electrical purposes; Rod and bars.

BS 2871 : Specification for copper and copper alloys. Tubes.

BS 2874 : Specification for copper and copper alloy rods and sections (other than

forging stock).

BS 4360 : Specification for weldable structural steel.

BS 6360 : Specification for conductors in insulated cables and cords.

BS 6651 : Protection of Structures against Lightning.

BS 6746 : Specification for PVC insulation and sheath of electric cables.

BS 7430 : Code of Practice for Earthing.

International Standards

ISO 427 : Wrought copper-tin alloys - chemical composition and forms of

wrought productions.

ISO 428 : Wrought copper-aluminum alloys - chemical composition and forms of

wrought productions.

ISO 11 87 : Special wrought copper alloys - chemical composition and forms of

wrought products.

ISO 1137 : Wrought coppers having minimum copper contents of 99.85% -

chemical composition and forms of wrought products. C. GENERAL

An earthing System generally in accordance with the requirements of IEEE 80 and BS 7430 shall be designed under this contract. Installation and supply of all materials and equipment also included. The earthing system shall also be including earth electrodes and connections to all electrical equipment and metallic structures on the site. The earth electrodes shall limit the potential rise under fault conditions and buried conductors shall be provided to

324

limit potential differences on the site and adjacent to the site to ensure safety to people and animals. Protection of all electrical equipment against lightning shall also be provided.

a. EXTENT OF WORK

The work under the clause "SUB-STATION EARTHING" comprises the site testing, design, supply and installation including excavation, back filling and temporary reinforcement of earthing system and connections to electrical apparatus at the substation. Also included the lightning protection scheme and the provision of portable earthing devices.

The contractor shall be required to undertake all necessary earth resistively tests at the sub-station sites and from the tests result to undertake the design of the earthing system. The design as well as providing safe passage to earth for the stated earth fault currents, shall also include calculation of step, touch and mesh potentials, which shall be within the allowable limits of the standards quoted in the specification.

The design calculations of step, touch and mesh potentials accompanied by full installation drawings and material requirement schedules, shall be submitted to and receive the approval of the Engineer before materials procurement or installation commences.

b. SOIL SURVEY

The preliminary tender design shall be based on a value of 100 ohm-m soil resistivity.

Not later than one month after the site has been handed over for access, the Contractor shall carry out an earth resistivity survey of the sites and report in writing to the Engineer in accordance with the approved program. The report shall detail the methods and instruments used and the results of the surveys. Based on the results the Contractor shall include in the report his proposal for the resistiveties to be used in the design of the earthing system.

The surveys shall show the variation of resistivity across the site and with the depth below the site. The Contractor shall consider if there is a need to model the resistivity in two layers and if there is any advantage in the use of deep rod electrodes.

The surveys shall also determine the depth and nature of any underlying rock, which may limit the depth for driving earth rods or if boring will be necessary for installing earth rods.

The weather conditions prior to and at the time of the surveys shall be recorded in the report and an assessment made of the seasonal variations in resistivity based on meteorological data for the area. The program for the project should, as far as possible, time the resistivity surveys to take place during a dry season.

The report should also state if there are any indications that the ground is corrosive to bare copper.

The report shall be approved by the Engineer before proceeding with the design of the earthing

c. FAULT CURRENT AND DURATION

Each site shall be provided with an earth grid of buried conductors designed for an earth fault current of 50 KA for one second. The preliminary earthing, design shall be such that the potential rise shall not exceed kV.

325

d. EARTH ELECTRODE SYSTEM DESIGN

i) Design Calculations

The design of the earth electrode systems shall be based on the approved earth resistivity data and the system fault currents and their duration.

The design calculations in detail shall be submitted for approval of the Engineer and shall be based on the methods given in the standards listed. The calculations shall include the following parameters:-

(a) earth resistance of the whole system and of its components.

(b) earth potential rise

(c) step, touch and mesh potentials inside and outside the perimeter fence

(d) requirements for a high resistance surface layer

(e) conductor ratings

Earthing points shall be provided such that the combined resistance of the earth grid and all other earthing points does not exceed 0.5 ohm during the dry season.

The earth potential rises shall not exceed the CHIT limits appropriate to the classification of the system unless special precautions are taken to cater for transferred potentials.

Step, touch and mesh potentials shall be within the permitted limits calculated in accordance with the standards given in IEEE 80 for the proposed surface layer.

ii) Earth Electrode

The earth electrode shall comprise a system of bare conductors forming a mesh buried near the surface of the ground and supplemented, if required, by one or more of the following electrodes:-

(a) a system of interconnected rods driven into the ground. (b) a mesh system of bare conductors buried in the ground. (c) structural metal work in direct contact with the ground. (d) reinforcing steel in buried concrete. (e) a system of bare conductors buried near the surface of the ground outside the

perimeter fence.

iii) Mesh System

The mesh system shall be designed with above to limit touch, step and mesh potentials taking into account the combined length of the mesh conductors, other buried conductors and rods but excluding any buried conductors outside the perimeter fence. Due regard shall be given to non-linear distribution of the fault current giving rise to the highest potentials at mesh corners.

The rating of the mesh conductors shall be compatible with the fault currents after allowing for parallel paths of hard drawn high conductivity copper strip with a minimum conductor size of 150 mm2.

326

The conductor shall be installed in trenches excavated by the contractor to a depth of 500 mm. The system will be installed after all foundations have been laid and the site filled to 100 mm below finished level. When the earthing grid has been laid and back filled, bricks will be laid up to finished site level. Where the excavated material is rocky or may be difficult to consolidate, the back filling shall be carried out using other material to the approval of the Engineer. The cost of such material shall be deemed to be included in the Contract. iv) Interconnected Rods

If the design calculations show that a mesh alone is unable to limit the required values, then the mesh shall be supplemented by the use of interconnected earthing rods driven into the ground or installed in bored holes.

Rods shall be installed inside the perimeter fence to enclose the maximum possible area compatible with the earthing of any metallic fence. (The spacing between rods shall not be less than their length, unless rating considerations determine otherwise). The copper rod electrodes of 15mm diameter shall be interconnected in groups of four to eight rods by insulated copper conductors and non-ferrous clamps to form a ring. Each group shall be connected to the mesh by duplicate insulated copper conductor via disconnecting test links.

Individual rods may be connected directly to the mesh, provided the rod can be disconnected for testing.

Rods installed in bored holes may be used to reach lower resistivity ground strata at depths beyond the reach of driven rods or where rock is encountered and it is not possible to drive rods. After installing the rod the bored hole shall be back-filled with a low resistivity liquid mixture, which shall not shrink after pouring, to ensure good contact between the rod and the ground for the life of the installation.

The resistance and rating of individual rods and the combined resistance of the groups of rods in the proposed design shall be calculated and the rating of the interconnecting conductors shall not be less than that of the group of rods with a minimum conductor size of 70 mm2.

The calculation of potentials in the design of the complete installation shall be made without the group of rods with the lowest estimated resistance to simulate the condition with the group disconnected for testing. v) Other Conductors

As an alternative to rods to supplement a mesh, additional bare copper conductors with a cross-section area of not less than 150mm2 may be used. They shall be buried in the ground within the perimeter fence to enclose the maximum possible area compatible with the earthing of any metallic fence. Such conductors may be laid below the mesh, below foundations or in areas where there is no plant. It shall be shown by calculation that the step potentials are low in such areas.

The conductor shall be in a ring, or a part of a ring, with at least two widely separated connections to the mesh or other parts of the earthing system.

vi) Reinforcing Steel

The reinforcing steel in the foundations of buildings containing the primary electrical equipment may be used as auxiliary electrodes, subject to the approval of the Engineer. The contractor shall show in the design calculations that the fault currents and d/c stray currents will not damage the structure.

327

Steel reinforcing mesh in the floors of the building may also be used for the control of step and touch potentials within the building subject to approval of the Engineer.

vii) Conductors Outside Perimeter Fence

If the design calculations show that the step and touch potentials outside the perimeter fence or wall exceed the limits, than additional bare conductors shall be buried in the ground outside the fence in the form of rings encircling the whole site.

The distance of the conductors from the fence and the depth shall be determined in the design to ensure that step and touch potentials are within the limits.

The minimum conductor size shall be 75mm2 copper and shall be connected to the fence or the mesh with 75mm2 conductors at each corner of the site and at intervals of not more than 100m. These conductors shall not be included in the calculations called for above.

H. DESIGN OF EARTH SYSTEM

I. i) Earth System

An earth system shall comprise the following components:-

(a) the conductors between the earth electrode system and the main earth bar (b) the main earth bar (c) the conductors between the main earth bar and the metallic frames,

enclosures or supports of electrical equipment (d) the conductors between structural metalwork and non-electrical equipment

and the main earth bar

The rating of earth system conductors connected between an item of electrical plant and the earth electrode system shall be sufficient to withstand the fault currents and duration, after allowing for the parallel paths through the earth system conductors, with any one conductor disconnected. The design comprising all the above mentioned items shall be submitted to the Engineer for approval within four months of the award of contract.

ii) Connection of the System Neutrals and Earth

The system neutral points within a substation shall be arranged in two groups with a conductor from earthing point.

The earth electrodes of a neutral earthing point shall be arranged in two groups with a conductor from each group to a test link and there shall be duplicate bare copper conductors of cross sectional area not less than 150 mm2 from each test link to the earth grid. The duplicate connection may be in the form of a ring.

Neutral earthing connections between the substation system (transformer) neutral and the test links shall be of bare copper tape, secured and supported on stand-off insulators so that there is no contact between copper tape and transformer tank.

Neutral earthing conductors shall normally be buried directly in the ground but where necessary, they may be cleared to walls, fixed to cable racks or laid in the cable trenches.

iii) Main Earth Bar

The main earth bar shall be in the form of a ring or rings of bare conductors surrounding, or

328

within an area in which items to be earthed are located. Where two or more rings are installed, they shall be interconnected by at least two conductors which shall be widely separated.

The main earth bar, or parts thereof, may also form part of the earth electrode system, providing this is bare conductor.

Each main earth bar shall be connected by at least two widely separated conductors to the earth electrode system.

The minimum conductor size for the main earth and interconnections between earth bars and the earth electrode system shall not be less than 150 mm2.

iv) Electrical Equipment Tank and Structure Connections to Earth

Connections between: (a) all HV electrical equipment and (b) LV electrical equipment comprising substantial multi-cubicle switchboards and the main earth bar shall be duplicated. The bare copper conductor size shall have a minimum cross section area of 150 mm2.

All substation equipment, including disconnectors, earth switched, main transformer tanks, current and voltage transformer tanks, switchboards, electrical supporting steelwork and gantries etc. shall all be connected with the earth grid.

Surge Arresters installed for the protection of transformers and reactors shall be connected by low reactance paths both to the transformer tanks and to the earth grid. Capacitor voltage transformers used in connection with line traps shall be connected by direct low reactance paths to a single earth rod for each Arrester, in addition to the earth grid.

An earth mat shall be installed at all operating positions for outdoor HV equipment manual operating mechanism boxes and local electrical control cubicles to ensure the safety of the operator. The mat shall be directly bonded to the cubicle and the conductors forming the mat and the bonding connection shall have a minimum copper cross-section area of 75 mm2.

Galvanized structures comprising bolted lattice components shall not be used as the sole earth connection path to post and strain insulators or to overhead line earth conductors.

Buildings containing electrical equipment shall be provided, at each level, with a ring of earthing conductors which shall have duplicate connections to the earth grid outside the building. The frames of all switchgear, control and relay panels and other electrical equipment and exposed structural metal work shall be connected by branches to a ring. The ring and branch conductors shall be of the same material as the earth grid. Strip run within buildings, inside cable trenches or above ground level on apparatus shall be neatly supported on non-ferrous clamps.

Fixed earthing connectors for use with portable earthing devices below shall be provided on each bus bar and on both sides of high voltage equipment is by tubular bus bars.

Rigid loops in the copper earthing strip branch bond between the equipment and the earthing grid shall be provided adjacent to each item of high voltage equipment for use with the portable earthing devices. The rigid loops shall be marked green.

329

Connections between other LV electrical equipment and the earth bar need not be duplicated. The single conductor shall be rated to withstand the fault rating of the equipment. v) Connections to Non-Electrical Structural Metalwork and Equipment

All metal work within the project area which does not form part of the electrical equipment shall be bonded to the main earth bar except where otherwise specified. The bonding conductor size shall be not less than 150 mm2.

Individual components of metallic structures of plant shall be bonded to adjacent components to form an electrically continuous metallic path to the bonding conductor.

Small electrically isolated metallic components mounted on non-conducting building fabric need not be bonded to the main earth bar.

I) MATERIALS AND INSTALLATION

J) i) Conductors

Conductors shall be of high conductivity copper in the form of circular conductors stranded to IEC 228(BS 6360) or solid rods or bars to BS 1433.

Conductor sheaths shall be of PVC to meet the requirements of BS 6746 Grade TM1 or IEC 502 Grade ST1 with a minimum thickness of 1.5mm.

Buried conductors which are not part of the earth electrode system shall be PVC sheathed circular stranded cable.

Bare strip conductors only shall be used for earth electrodes or voltage control meshes.

Conductors buried in the ground shall normally be laid at a depth of 500 mm in an excavated trench. The back fill in the vicinity of the conductor shall be free of stones and the whole back fill shall be well consolidated. Conductors not forming part of a voltage control mesh shall be laid at the depth required by the approved design and in the case of a PVC sheathed conductor, at the same depth as any auxiliary power or control cables following the same route.

All conductors not buried in the ground shall be straightened immediately prior to installation and supported clear of the adjacent surface.

ii) Earth Rods

Earth rods shall be driven to a depth below the ground water table level, to be determined by the Contractor during soil investigation and survey of site.

The earth rods shall be of hard-drawn high conductivity copper with a diameter of not less than 15mm with hardened steel driving caps and tips. The rods should be as long as possible but couplings may be used to obtain the overall depth of driving required by the design.

The rods shall be installed by driving into the ground with a power hammer of suitable design to ensure the minimum of distortion to the rod. Where it is not possible to drive rods to the full depth required due to the presence of a strata of rock, then holes shall be drilled or blasted in the rock. The holes shall be filled with betonies or other approved material prior to inserting the rod.

330

If difficult driving conditions arising from hard or rocky ground are encountered or are anticipated or there is a need for deep rods, then high tensile steel rods shall be used. High tensile steel rods shall have a molecularly bounded high conductivity copper coating with a minimum radial thickness of not less than 0.25 mm. The overall diameter shall be not less than 12 mm. Rolled external screw threads shall be used on the rod for coupling and after rolling the thickness of the copper coating on the threaded portion shall be not less than 0.05 mm.

Rods, driving caps and tips shall about at couplings to ensure that the couplings and screw threads are not subject to driving forces. All screw threads shall be fully shrouded at the couplings. Alternatively, conical couplings may be used to the approval of the Engineer.

High conductivity copper for earth rods shall have a minimum copper content (including silver) of 99.90% to ISO 1337, Cu-ETP or Cu-FRHS (BS 2894 Grade C 101 or C102) for copper earth rods and to ISO 1337 Grade Cu-ETP (BS 28734 Grade C 101) for the molecular bonded copper coating of steel rods.

The steel for copper-clad steel rods shall be low carbon steel with a tensile strength of not less than 570 N/mm2 to ISO 630, Grade Fe 430A (BS 4360 Grade 43A) or better.

Couplings for copper rods shall be of 5% phosphor bronze (copper-tin-phosphorous) to ISO 427, CU Sn4 (BS 2874, Grade PB 102M) and for copper bonded steel rods of 3% silicon or 7% aluminum bronze to BS 2874, Grade CS 101 and BS 2871, Grade CA 102.

iii) Fittings

Clips supporting strip conductors not buried in the ground shall be of the direct contact type and clips for circular conductors shall be of the cable saddle type. The clips shall support the conductors clear of the structure.

Conductors shall be connected to earth rods by a bolted clamp to facilitate removal of the conductor for testing rod.

Disconnecting links shall comprise a high conductivity copper link supported on two insulators mounted on a galvanized steel base for bolting to the supporting structure. The two conductors shall be in direct contact with the link and shall not be disturbed by the removal of the link. Links for mounting at ground level shall be mounted on bolts embedded in a concrete base.

Disconnecting links mounted at ground level and the connections at the earth rods shall be enclosed in concrete inspection pits, with concrete lids, installed flush with the ground level.

All conductor fittings shall be manufactured from high strength copper alloys with phosphor bronze nuts, bolts, washers and screws. Binary brass copper alloys will not be acceptable. All fittings shall be designed for the specific application and shall not be permanently deformed when correctly installed.

Sheathed conductor support fittings may be of silicon aluminum, glass-filed nylon or other tough non-hygroscopic material for indoor installations.

Fittings not in direct contact with bare or sheathed conductors may be of hot-dip galvanized steel. Bi-metallic connectors shall be sued between conductors of dissimilar materials and insulating material shall be interposed between metallic fittings and structures of dissimilar

331

materials to prevent corrosion. iv) Joints Permanent joints shall be made by exothermic welding (Cad Welding) below ground, or crimping for above ground connections.

Detachable joints shall be bolted and stranded conductors at bolted joints shall be terminated in exothermic welded lugs or a crimped cable socket. The diameter of any holes drilled in strip conductors shall not greater than half the width of the strip.

Connections to electrical equipment shall be detachable and made at the earthing studs or bolts provided on the equipment by the manufacturer. When an earthing point is not provided, the point and method of connection shall be agreed with the Engineer.

Connections to metallic structures for earthing conductors and bonding conductors between electrically separate parts of a structure shall be either by direct exothermic welding or by bolting using a stud welded to the structure. Drilling of a structural member for a directly bolted connection shall only be carried out to the approval of the Engineer.

Bolted joints in metallic structures, including pipe work and which do not provide direct metallic contact, shall either be bridged by a bonding conductor or both sides of the joint shall be separately bonded to earth, unless the joint is intended to be and insulated joint for cathodic protection or other purposes.

When the reinforcing in concrete is used as a part of the earthing system, the fittings used to provide a connection point at the surface of the concrete shall be exothermically welded to a reinforcing bar. This fitting shall be provided with a bolted connection for an earthing conductor. The main bars in the reinforcing shall be welded together at intervals to ensure electrical continuity throughout the reinforcing.

No connections shall be made to reinforcing bars and other steelwork which do not form part of the earthing system and are completely encased in concrete.

J. EARTHING OF FENCES

i) Method

Metallic fences shall be separately earthed unless they come within 1.8m of any equipment of structure above the surface of the ground and which is connected to the main earthing system. If the separation of 1.8m cannot be obtained, the fence shall be bonded to the main earthing system.

ii) Separately Earthed Fences

The earthing of a fence shall be provided by connecting certain metallic fence posts to an earth rod by a copper conductor. The earth rod shall be driven adjacent to the posts inside the fence line to a depth of not less than 3.0m. where no metallic posts are provided, the earth rods shall be connected directly to the metal wires, mesh or other components of the fence.

If, owing to the nature of the ground, it is not possible to drive earth rods, then fence posts shall be connected to the center point of a 20m length of bare copper conductor buried in the ground at a depth of 500mm, running closely parallel to the inside of the fence.

The earth rods or bare conductor electrodes shall be installed at each corner post, below the

332

outer phase conductors of overhead line connections passing over the fence, at each gate and at intervals of not more than 100m. iii) Bonded Fences

Fences which need to be bonded to the main earthing system of the installation shall be connected by copper conductors to the nearest accessible point on the main earthing system at each point where the fence comes within 1.8 m of any electrical equipment. Bonds shall also be made to each corner post, below the outer phase conductors of overhead line connections passing over the fence at each gate and at intervals of not more than 100m.

iv) Bonding of Fence components

Fences made up bolted steel or other metallic component do not require bonding between components. Where such fences have non-metallic component, bonds shall be installed to maintain continuity between metallic components. Reinforced concrete components shall be treated as being non-metallic.

Longitudinal wires for supporting other fence component or for anti-climbing guards and the wires of chain link, shall be directly bonded to each electrode or to each bond to the main earthing system.

Metallic component on masonry, brick, concrete or similar boundary wall shall be treated in the same manner as metallic fences.

Wire fence component coated for anticorrosion protection shall be earthed inn accordance with this clause.

v) Gates

The fixed metallic components on both sides of the gate shall be directly bonded together by a copper conductor installed under the surface of the access way. Flexible conductors shall be installed to bond the moving parts of the gates to the metallic fixed parts. An earth rod or a bond to the main earthing system shall be installed at each gate.

vi) Potential Control Outside Fences

Where the approved design calculations show that the touch or step potentials outside the fence or boundary wall would otherwise be excessive, bare copper conductors shall be buried in the ground outside the fence or boundary wall at such depths and spacing as are shown in the approved design calculations to give acceptable touch and step potentials. The conductors shall form complete rings surrounding the installation and each ring shall be bonded to the adjacent ring and to the fence at each corner, below the outer phase conductors of overhead line connections passing over the fence at each gate and at intervals of not more than 100 m. In this case separate earth electrodes are not required for the fences.

If the boundary fence or wall is substantially non-metallic, the rings of conductors shall be bonded to the main earth system at each corner of the site and at intervals of not more than 100m. Any metallic components on such boundary fences or walls shall be bonded to the earthing system in accordance with this Specification.

If the boundary fence is metallic and is not within 1.8 m of any part of the main earthing system or equipment bonded thereto, the fence and outer conductor rings shall but be connected to the main earthing system unless the approved design calculations show

333

otherwise. Any meshes formed by bonding the outer conductors to he main earthing system shall be sub-divided by additional conductors, if required, to give acceptable touch, step and mesh potentials.

vii) Conductors

All conductors used for earthing and bonding the fences and components and for outer rings shall have a cross-sectional area of not less than 70 mm2.

vii) Portable earthing devices

Portable earthing devices for use with outdoor 33 KV apparatus in substations shall be supplied in the numbers stated in Schedule of Technical Requirements and shall comprise:

(a) Copper alloy earth end clamp for connection to the rigid loops in equipment earth

bonding connections. (b) Aluminum ally line and bus bar end clamp to suit the type supplied under the Contract. (c) Flexible stranded aluminum alloy conductor with clear protective PVC sheath, size

suitable for the specified fault level and duration. (d) Telescopic operating pole of glass fibre or similar material, of sufficient length to reach

the height of connections to high voltage equipment from ground, but retractable into a carrying length not exceeding 2.5m, and complete with non-slip hand grips.

K. SUB-STATION EARTHING AND EARTHING ERECTION

General earthing of all equipment shall be in accordance with the IEC recommendation No. 80 :1976-Guide for safety in alternating current sub-station Grounding, the British standard code of practice CP-1013: 1965 or other approved standard.

i) Earthing System

Each site shall be provided with an earth grid of buried copper strip conductors designed for an earth fault current of 25 KA for 3 seconds for all S/S. For the purpose of preliminary design it shall be assumed that the distribution of the fault current will be such that the potential rise of each site will not exceed 5 KV.

The preliminary design shall be based on clay silt having an assumed resistively of 50 ohm meters.

Step and touch voltages both inside and outside the station shall not exceed 50 V.

The design of earth grid over the area occupied by switchgear and associated apparatus shall be based on a maximum grid spacing of 5m x 5m. Conductors shall be buried at 800mm depth.

Earthing points will be provided so that the combined resistance of the earth grid and earthing points shall be less than 1.0 ohm under any climatic conditions.

The operating mechanisms of isolators, earth switches and circuit breaker kiosks not integral with the circuit breaker shall be connected to the earth system by a branch entirely separate from that employed to earth their bases. The branch is to be installed such that the connection would pass beneath where and operator would stand, so as to minimize step potential.

334

Fences shall be earthed independently of the sub-station grid.

Connections to plant and equipment shall be made using the earthing terminals specified in the contract where a strip has to be drilled to fit an earth terminals the diameter of the hole shall not be greater than ½ the width of the strip.

Joints in earthing strip shall employ chemical welding or high compression joints or clamps.

ii) Earthing Electrode

Each Earhting point shall consist of a group of copper rods drawn into undisturbed soil to a minimum depth of 4m. Each copper electrode shall be complete with approved non ferrous clamps for the connection of earthing conductors and with a hardened steel tip and cap for driving by means of a power hammer. The number of electrodes per group shall be not less than four and not more than eight, 16mm diameter rods and each copper electrode rod shall be 4 meter length and the number of rod groups per sub-station have been declared in the price schedule.

The electrodes of an earthing point will be arranged in two sub-groups with a conductor from each sub-group to the test link of the earth grid.

In addition to the above a single electrode is to be driven as close as possible and connected to the following :

i) Three phase set of surge diverts.

ii) Three phase set of voltage transformers.

iii) Three phase set of power transformers. iv) The fence where an overhead line crosses at gates and at fence corners. The distance

between electrodes is not to exceed 50 m.

iii) Insulated Earthing Conductors

Conductors for interconnection between the electrodes in any group and between groups and the connections between the link chambers and sub-station earthing main grid shall have twin conductors with a combined rating of 25 KA for three seconds for all S/S . The neutral points of the 11 KV system shall be connected to the link chamber with twin conductors as above.

Earthing conductors shall be of annealed high conductivity copper and shall be stranded in accordance with IEC-228 table VII class-2. They shall be protected with an extruded PVC sheath of 100 volts grade.

iv) Sub-station Earthing Screen

Approved earth screens shall be provided to protect the equipment from direct lightning strikes. The screens shall be of the steel corned aluminum wires of not less than 35 Sq.mm total cross section and connected to provide low impedance paths to earth.

The layout of the earth wires shall be such that generally equipment to be protected lie within areas bounded by lines drawn from the earth wire at 35 degree to the vertical in a plane perpendicular to the axes of the earth wire. The earth screen shall be suitable for

335

extension to protect the sub-station equipment to be installed in suitable stages of development.

Connections shall be made of copper strip of 150 Sq.mm cross section between each support for the overhead earthed screen wire and the main sub-station earthing system. Earth wires shall be held in clamps with free pin type joints between clamps and supports connections shall be provided for the terminations of the earth wires of the overhead lines including bimetal connectors where necessary.

The necessary stays, fittings, anchors, flying stays and additional masts shall ensure clearance of not less than 4600 mm over roadways for circuit breaker or transformer removal. The design of all structures shall ensure that in the event of breakage of either one earth wire or one stay wire the factor or safety is not less than 1.5.

L. REQUIREMENT EARTHING

i) 11 kV Switchgear

All metal parts including any relay instrument etc. mounted on the switchboard shall be connected to a copper earth bar which runs along the full length of the switchboard.

The cross section to the bar shall be sufficient to carry the rated short time withstand current of the switchgear for three seconds.

The frame of the draw-out circuit breakers shall be connected to the earth bar through a substantial plug type contact.

ii) Low Voltage Switchboards

Earth metal of switchboards fuse and distribution boards and distribution boards shall be bonded together and earthed to the main sub-station earthing system. Earthing connections shall be carried out in bare copper strip having a 3 second rating not less than 25 KA for all S/S

iii) Control Panels

Each control panel shall be provided with a copper earth bar of not less than 80 Sq.mm cross-section and arranged so that the bars of adjacent panels can be joined together to from a common bus.

The common earthing bus bar of control and relay panels shall be connected to the main station earthing systems via a copper earthing connection of not less than 80 Sq.mm.

iv) Neutral Earthing

The 11 KV neutral of the 33/11 KV transformer shall incorporate provision for the scheduled current transformers and shall be directly connected to the main station earthing system. The connection shall be formed of twin conductors and shall be capable to carrying 30 KA for 3 (Three) seconds for all S/S.